clk: renesas: rzg2l: Remove critical area

The spinlock in rzg2l_mod_clock_endisable() is intended to protect
RMW-accesses to the hardware register.  There is no need to protect
instructions that set temporary variables which will be written
afterwards to a hardware register.  With this only one write to one
clock register is executed thus locking/unlocking rmw_lock is removed.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230929053915.1530607-7-claudiu.beznea@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>