dm mirror log: round up region bitmap size to BITS_PER_LONG

In the Linux kernel, the following vulnerability has been resolved: dm mirror log: round up region bitmap size to BITS_PER_LONG The code in dm-log rounds up bitset_size to 32 bits. It then uses find_next_zero_bit_le on the allocated region. find_next_zero_bit_le accesses the bitmap using unsigned long pointers. So, on 64-bit architectures, it may access 4 bytes beyond the allocated size. Fix this bug by rounding up bitset_size to BITS_PER_LONG. This bug was found by running the lvm2 testsuite with kasan.