mfd: ti_am335x_tscadc: Rename the subsystem enable macro

This bit is common to all devices (ADC, Touchscreen, Magnetic reader) so
make it clear that it can be used from any location by operating a
mechanical rename:
s/CNTRLREG_TSCSSENB/CNTRLREG_SSENB/

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20211015081506.933180-31-miquel.raynal@bootlin.com