regulator: pca9450: Fix BUCK2 enable_mask

This fixes a copy & paste error.
No functional change intended, BUCK1_ENMODE_MASK equals BUCK2_ENMODE_MASK.

Fixes: 0935ff5f

 ("regulator: pca9450: add pca9450 pmic driver")
Originally-from: Robin Gong <yibin.gong@nxp.com
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Link: https://lore.kernel.org/r/20230512081935.2396180-1-alexander.stein@ew.tq-group.com
Signed-off-by: Mark Brown <broonie@kernel.org>