wifi: ath9k: Remove error checks when creating debugfs entries

wifi: ath9k: Remove error checks when creating debugfs entries

We should not be checking the return values from debugfs creation at all: the
debugfs functions are designed to handle errors of previously called functions
and just transparently abort the creation of debugfs entries when debugfs is
disabled. If we check the return value and abort driver initialisation, we break
the driver if debugfs is disabled (such as when booting with debugfs=off).

Earlier versions of ath9k accidentally did the right thing by checking the
return value, but only for NULL, not for IS_ERR(). This was "fixed" by the two
commits referenced below, breaking ath9k with debugfs=off starting from the 6.6
kernel (as reported in the Bugzilla linked below).

Restore functionality by just getting rid of the return value check entirely.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=219122
Fixes: 1e4134610d93 ("wifi: ath9k: use IS_ERR() with debugfs_create_dir()")
Fixes: 6edb4ba6fb5b ("wifi: ath9k: fix parameter check in ath9k_init_debug()")
Reported-by: Daniel Tobias <dan.g.tob@gmail.com>
Tested-by: Daniel Tobias <dan.g.tob@gmail.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20240805110225.19690-1-toke@toke.dk