ext4: fix mount failure with quota configured as module

ext4: fix mount failure with quota configured as module

BugLink: https://bugs.launchpad.net/bugs/1868665
When CONFIG_QFMT_V2 is configured as a module, the test in
ext4_feature_set_ok() fails and so mount of filesystems with quota or
project features fails. Fix the test to use IS_ENABLED macro which
works properly even for modules.

Link: https://lore.kernel.org/r/20200221100835.9332-1-jack@suse.cz
Fixes: d65d87a07476 ("ext4: improve explanation of a mount failure caused by a misconfigured kernel")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
(cherry picked from commit 9db176bceb5c5df4990486709da386edadc6bd1d)
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Andrea Righi <andrea.righi@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>