arm: dma-mapping: WARN_ON if iova is not 128M aligned

Enforce 128M alignment on the IOVA for the proper virtual address to
be returned by the bitmap_() API's through alloc_iova(). The current
implementation causes the bitmap index search out of bounds of a page if
not 128M aligned.

Change-Id: Ie57ca0b7465c91d318145ed270b7d47d822c8eeb
Fixes:I88ddd98a76b ("arm/arm64: dma-mapping: Fix iova region size")
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>