wifi: mt76: mt7915: add error message in mt7915_thermal_set_cur_throttle_state()

wifi: mt76: mt7915: add error message in mt7915_thermal_set_cur_throttle_state()

[ Upstream commit 2f2d86309e228adfe658c9c0a23c726d8b3ce475 ]

Add dev_err so that it is easier to see invalid setting while looking at
dmesg.

Co-developed-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Howard Hsu <howard-yh.hsu@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Stable-dep-of: 9c97df11dfe6 ("wifi: mt76: mt7915: rework init flow in mt7915_thermal_init()")
Signed-off-by: Sasha Levin <sashal@kernel.org>