LIB: Add bitmap_find_next_zero_area_off()

This commit adds a bitmap_find_next_zero_area_off() function which
works like bitmap_find_next_zero_area() function expect it allows an
offset to be specified when alignment is checked.  This lets caller
request a bit such that its number plus the offset is aligned
according to the mask.

Change-Id: Ib0593cf578ed69ba4c51b1e102a1f8ea1aeb93e8
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Larry Bassel <lbassel@codeaurora.org>