ARM: EXYNOS: change the PHYSMEM_BITS and SECTION_SIZE

On EXYNOS5440 there is DRAM on the 36-bit address range. Hence
this patch converts the MAX_PHYSMEM_BITS macro to 36 if LPAE is
enabled for the ARM architecture.

The conventional section size on EXYNOS is 256M due to sparsemem.
Since EXYNOS5440 has memory in multiples of 1G in 32-bit and 36-bit
range, this has now been modified to 31.

Signed-off-by: Subash Patel <subash.rp@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>