ALSA: emu10k1: fix locking in snd_emu1010_fpga_link_dst_src_write()

This is a multi-register operation, which must be locked in its
entirety.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230428095941.1706278-5-oswald.buddenhagen@gmx.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>