ath11k: Handle errors if peer creation fails

ath11k: Handle errors if peer creation fails

[ Upstream commit c134d1f8c436d96b3f62896c630278e3ec001280 ]

ath11k_peer_create() is called without its return value being checked,
meaning errors will be unhandled. Add missing check and, as the mutex is
unconditionally unlocked on leaving this function, simplify the exit
path.

Addresses-Coverity-ID: 1497531 ("Code maintainability issues")
Fixes: 701e48a43e15 ("ath11k: add packet log support for QCA6390")
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201004100218.311653-1-alex.dewar90@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>