pinctrl: renesas: r8a77990: Drop bogus PUEN_ prefixes in comments

The "PUEN_" prefixes are part of the bit names of the PUEN registers,
while the comments should refer to the actual pin names.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/9ea85ae8973f6d9b3d10f02f0d9b4ab6a086ec63.1619785375.git.geert+renesas@glider.be