ARM: mm: Remove bootmem code and switch to NO_BOOTMEM

Now with dma_mask series merged and max*pfn has consistent meaning on ARM
as rest of the arch's thanks to RMK's mega series, lets switch ARM code
to NO_BOOTMEM. With NO_BOOTMEM change, now we use memblock allocator to
reserve space for crash kernel to have one less dependency with nobootmem
allocator wrapper.

Tested with both flat memory and sparse (faked) memory models with highmem
enabled.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>