arm: Partial cleanup and audit usage of <config.h>

We need to include <config.h> directly when a file needs to have
something such as CFG_SYS_SDRAM_SIZE referenced as this file is not
automatically globally included and is most commonly indirectly included
via common.h.  Remove most cases of arm including config.h directly, but
add it where needed. This includes a few board-specific fixes.

Signed-off-by: Tom Rini <trini@konsulko.com>