mm: cma: fix incorrect type conversion for size during dma allocation.

This was found during userspace fuzzing test when a large size dma cma
allocation is made by driver(like ion) through userspace.

  show_stack+0x10/0x1c
  dump_stack+0x74/0xc8
  kasan_report_error+0x2b0/0x408
  kasan_report+0x34/0x40
  __asan_storeN+0x15c/0x168
  memset+0x20/0x44
  __dma_alloc_coherent+0x114/0x18c

Change-Id: Ia0c4def2ec27ec56e9faf43ed1b8012381e3b253
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 67a2e213e7e937c41c52ab5bc46bf3f4de469f6e
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[shashim@codeaurora.org: replace %p by %pK in print format]
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>