twl4030-irq.c: fix compiler warning due to raw-spinlock conversion

Commit 239007b8

 ("genirq: Convert irq_desc.lock to raw_spinlock")
seems to have missed this driver, leaving it to use the normal spin-lock
functions for the irq descriptor lock, which is now a raw lock.

Reported-and-compile-tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>