iio: adc: rzg2l_adc: Fix typo

Fix typo RZG2L_ADSMP_DEFUALT_SAMPLING -> RZG2L_ADSMP_DEFAULT_SAMPLING.

Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
Link: https://lore.kernel.org/r/20220107172529.12361-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>