can: tcan4x5x: replace depends on REGMAP_SPI with depends on SPI

regmap is a library function that gets selected by drivers that need it. No
driver modules should depend on it. Instead depends on SPI and select
REGMAP_SPI. Depending on REGMAP_SPI makes this driver only build if another
driver already selected REGMAP_SPI, as the symbol can't be selected through the
menu kernel configuration.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: http://lore.kernel.org/r/20200413141013.506613-1-enric.balletbo@collabora.com
Reviewed-by: Dan Murphy <dmurphy@ti.com>
Fixes: 5443c226

 ("can: tcan4x5x: Add tcan4x5x driver to the kernel")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>