ext4: fix compile error while opening the macro DOUBLE_CHECK
the error is:
fs/ext4/mballoc.c:475:43: error: 'struct ext4_group_info' has
no member named 'bb_bitmap'.
so, the definition of macro DOUBLE_CHECK should before
'struct ext4_group_info', I fixed it, and I moved the macro
AGGRESSIVE_CHECK together, because I think they shoule be together.