pinctrl: sh-pfc: Absorb enum IDs in PINMUX_CFG_REG_VAR() macro

Currently the PINMUX_CFG_REG_VAR() macro must be followed by
initialization data, specifying all enum IDs.  Hence the macro itself
does not know anything about the enum IDs, preventing the macro from
performing any validation on it.

Make the macro accept the enum IDs as a parameter, and update all users.
Note that array data enclosed by curly braces cannot be passed to a
macro as a parameter, hence both the register field widths and the enum
IDs are wrapped using the GROUP() macro.

No functional changes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>