pinctrl: sh-pfc: rcar-gen3: Fix grammar in static pin comments

The comment block explaining the rationale for static pins contains
grammar errors.  It appeared first in the pin control driver for R-Car
H3 ES1.x, and spread to R-Car M3-W, H3 ES2.0, and M3-N later.

Fix the grammar in all copies at once.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>