pinctrl: sh-pfc: r8a7794: Remove bogus IPSR9 field

The Peripheral Function Select Register 9 contains 12 fields, but the
variable field descriptor contains a 13th bogus field of 3 bits.

Fixes: 43c4436e ("pinctrl: sh-pfc: add R8A7794 PFC support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>