hw/display/sm501: Always map the UART0

hw/display/sm501: Always map the UART0

The SM501 is a Mobile Multimedia Companion Chip with 2 UARTs.
This model only implements the first UART. Being part of the
chipset, the UART block is always mapped in memory, regardless
of whether we provide a chardev backend.

Since commit 12051d82f, qemu_chr_fe_init() accepts a NULL chardev.
Let's remove the chardev check and always map the UART in the
chipset memory.

Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Message-Id: <20191122133623[email protected]>
Reviewed-by: Peter Maydell <[email protected]>