serial: sirf: Fix compilation failure

After 07d410e0) serial: sirf: fix spinlock deadlock issue it is no longer
possiblet to compile this driver. The rename of one of the spinlocks is
faulty. After looking at the original patch I believe this is the correct
fix.

Compile tested using ARM's multi_v7_defconfig

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Acked-by: Barry Song <baohua@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>