recovery: update mkfs.f2fs args to match f2fs-tools 1.8.0

mkfs.f2fs in 1.8.0 returns error if number of sectors is 0. Skip
this argument to let mkfs detect device size. 0 sector is also not
necessary for 1.4.1.

Test: format userdata to f2fs and boot
Bug: 37758867
Change-Id: If120988dfb678596c973d183572f870eb0b72a27