Remove CROSS_COMPILE default from arch/*/config.mk

Remove CROSS_COMPILE default from arch/*/config.mk

In order to support the compiler providing information used within
Kconfig itself we cannot have the compiler be determined by
arch/*/config.mk as we will not be able to evaluate that yet.  Given
that most documentation tells people to specify CROSS_COMPILE, remove
these references.

Cc: Huan Wang <[email protected]>
Cc: Angelo Dureghello <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Rick Chen <[email protected]>
Cc: Thomas Chou <[email protected]>
Cc: Wolfgang Denk <[email protected]>
Cc: Marek Vasut <[email protected]>
Cc: Nobuhiro Iwamatsu <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Bin Meng <[email protected]>
Cc: Max Filippov <[email protected]>
Signed-off-by: Tom Rini <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Acked-by: Michal Simek <[email protected]>