ion: use correct section map size for LPAE

Use correct section map size for LPAE. At present ion use
CONFIG_IOMMU_IO_PGTABLE_ARMV7S to determine whether to use LPAE or short
descriptor section size.  This is insufficient. Check for CONFIG_64bit and
CONFIG_LPAE as well to decide correct section size.

Change-Id: If730d98da110ebb338f7f1affccaae28c0c58a9e
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>