memory: ti-gpmc: Fix build

sys_proto.h no longer exists for K3 platform so drop it.
Include sizes.h to so SZ_16M is visible.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://www.mail-archive.com/u-boot@lists.denx.de/msg499176.html


Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>