wifi: mt76: mt7996: ensure 4-byte alignment for beacon commands

[ Upstream commit 5d197d37 ]

If TLV includes beacon content, its length might not be 4-byte aligned.
Make sure the length is aligned before sending beacon commands to FW.

Signed-off-by: Benjamin Lin <benjamin-jw.lin@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Stable-dep-of: 9e461f4a ("wifi: mt76: mt7996: fix uninitialized TLV data")
Signed-off-by: Sasha Levin <sashal@kernel.org>