can: ti_hecc: Replace platform dependency with ARM dependency

OMAP's ti_hecc driver is used to support the CAN controller on many omap2plus
SoCs (OMAP2430, OMAP3, OMAP4, OMAP5 and AM335x), so it's wrong to make this
depend on OMAP3 only. Take an extra step, to get wider build coverage, and make
the driver depend on ARM.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>