ext4: remove unneeded test of ret variable

Currently in ext4_fallocate() and ext4_zero_range() we're testing ret
variable along with new_size. However in ext4_fallocate() we just tested
ret before and in ext4_zero_range() if will always be zero when we get
there so there is no need to test it in both cases.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>