ARM: 7864/1: Handle 64-bit memory in case of 32-bit phys_addr_t

Use CONFIG_ARCH_PHYS_ADDR_T_64BIT to determine
if ignoring or truncating of memory banks is
neccessary. This may be needed in the case of
64-bit memory bank addresses but when phys_addr_t
is kept 32-bit.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>