pinctrl: sh-pfc: sh73a0: Fix fsic_spdif pin groups

There are two pin groups for the FSIC SPDIF signal, but the FSIC pin
group array lists only one, and it refers to a nonexistent group.

Fixes: 2ecd4154 ("sh-pfc: sh73a0: Add FSI pin groups and functions")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>