mkfs.f2fs: support large sector size

mkfs.f2fs: support large sector size

Since f2fs support large sector size in commit 55cf9cb63f0e "f2fs: support large
sector size", block device with sector size of 512/1024/2048/4096 bytes can be
supported.

But mkfs.f2fs still use default sector size: 512 bytes as sector size, let's fix
this issue in this patch.

v2:
 o remove unneeded printed message when sector size is large than 512 bytes
   suggested by Kinglong.
 o show correct sector size in printed message.
 o use config.sectors_per_blk instead of DEFAULT_SECTORS_PER_BLOCK suggested by
   Kinglong.
v3:
 o remove another unneeded printed message when sector size is large than 512
   bytes suggested by Kinglong.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Reviewed-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>