Kconfig: Change SYS_MALLOC_F_LEN default to 0x2000

Kconfig: Change SYS_MALLOC_F_LEN default to 0x2000

The most commonly used value today is 0x2000 and not 0x400.  Rework the
Kconfig logic to use this more frequently used value as the default.

Cc: Andrew F. Davis <[email protected]>
Cc: Alex Nemirovsky <[email protected]>
Cc: Alexey Brodkin <[email protected]>
Cc: Alison Wang <[email protected]>
Cc: Anastasiia Lukianenko <[email protected]>
Cc: Andes <[email protected]>
Cc: Andre Przywara <[email protected]>
Cc: Bharat Gooty <[email protected]>
Cc: David Lechner <[email protected]>
Cc: Dzmitry Sankouski <[email protected]>
Cc: Enric Balletbo i Serra <[email protected]>
Cc: Eugeniy Paltsev <[email protected]>
Cc: Fabio Estevam <[email protected]>
Cc: Gerald Kerma <[email protected]>
Cc: Gregory CLEMENT <[email protected]>
Cc: Holger Brunck <[email protected]>
Cc: Jaehoon Chung <[email protected]>
Cc: Jassi Brar <[email protected]>
Cc: Kristian Amlie <[email protected]>
Cc: Krzysztof Kozlowski <[email protected]>
Cc: Liviu Dudau <[email protected]>
Cc: Luka Perkov <[email protected]>
Cc: Lukasz Majewski <[email protected]>
Cc: Marek Vasut <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Matthias Brugger <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Walle <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Minkyu Kang <[email protected]>
Cc: Nikita Kiryanov <[email protected]>
Cc: Nobuhiro Iwamatsu <[email protected]>
Cc: Oleksandr Andrushchenko <[email protected]>
Cc: Otavio Salvador <[email protected]>
Cc: Patrice Chotard <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Paul Kocialkowski <[email protected]>
Cc: Priyanka Jain <[email protected]>
Cc: Rajesh Bhagat <[email protected]>
Cc: Rayagonda Kokatanur <[email protected]>
Cc: Sergey Temerkhanov <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Stefan Bosch <[email protected]>
Cc: Stephan Gerhold <[email protected]>
Cc: Tetsuyuki Kobayashi <[email protected]>
Cc: Thomas Chou <[email protected]>
Cc: Thomas Fitzsimmons <[email protected]>
Cc: Thomas Weber <[email protected]>
Cc: Tony Dinh <[email protected]>
Cc: Trevor Woerner <[email protected]>
Cc: Vitaly Andrianov <[email protected]>
Cc: Vladimir Zapolskiy <[email protected]>
Cc: liuhao <[email protected]>
Cc: lixinde <[email protected]>
Cc: shuyiqi <[email protected]>
Cc: weichangzheng <[email protected]>
Signed-off-by: Tom Rini <[email protected]>
Reviewed-by: Thomas Chou <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Reviewed-by: Tony Dinh <[email protected]>
Reviewed-by: Patrice Chotard <[email protected]>
Reviewed-by: Kristian Amlie <[email protected]>