ARM: at91: pm: fix MCKx restore routine

ARM: at91: pm: fix MCKx restore routine

The at91_mckx_ps_restore() assembly function is responsible for setting
back MCKx system bus clocks after exiting low power modes.

Fix a typo and use tmp3 variable instead of tmp2 to correctly set MCKx
to previously saved state.
Tmp2 was used without the needed changes in CSS and DIV. Moreover the
required bit 7, telling that MCR register's content is to be changed
(CMD/write), was not set.

Fix function comment to match tmp variables actually used.

Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Fixes: 28eb1d40fe57 ("ARM: at91: pm: add support for MCK1..4 save/restore for ulp modes")
Link: https://lore.kernel.org/r/20250827145427.46819-3-nicolas.ferre@microchip.com
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
[claudiu.beznea: s/sate/state in commit description]
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>