i3c: dw-i3c-master: convert spinlock usage to scoped guards

i3c: dw-i3c-master: convert spinlock usage to scoped guards

Convert dw-i3c-master to use scoped spinlock guards in place of
open-coded spin_lock_irqsave()/spin_unlock_irqrestore() pairs to ensure
locks are always safely released on scope exit.

Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@altera.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/79020c006c15dda9d057946530f16cfb4650d450.1769479330.git.adrianhoyin.ng@altera.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>