ARM: 8903/1: ensure that usable memory in bank 0 starts from a PMD-aligned address

The calculation of memblock_limit in adjust_lowmem_bounds() assumes that
bank 0 starts from a PMD-aligned address. However, the beginning of the
first bank may be NOMAP memory and the start of usable memory
will be not aligned to PMD boundary. In such case the memblock_limit will
be set to the end of the NOMAP region, which will prevent any memblock
allocations.

Mark the region between the end of the NOMAP area and the next PMD-aligned
address as NOMAP as well, so that the usable memory will start at
PMD-aligned address.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>