rtc: renesas-rtca3: Fix typo in rtca3_ppb_per_cycle documentation

rtc: renesas-rtca3: Fix typo in rtca3_ppb_per_cycle documentation

Correct a typo in the kernel-doc comment for struct
rtca3_ppb_per_cycle by fixing "adjutment" to "adjustment".

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com> # on RZ/G3S
Link: https://patch.msgid.link/20260602192559.1791344-5-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>