ext4: consolidate checks for resize of bigalloc into ext4_resize_begin

Two different places checked for attempts to resize a filesystem with
the bigalloc feature. Move the check into ext4_resize_begin, which both
places already call.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/bee03303d999225ecb3bfa5be8576b2f4c6edbe6.1623093259.git.josh@joshtriplett.org


Signed-off-by: Theodore Ts'o <tytso@mit.edu>