board: ti: dra7xx: Select MCAN instead of DCAN on DRA76 EVM

board: ti: dra7xx: Select MCAN instead of DCAN on DRA76 EVM

MCAN can be accessed via DCAN1 or DCAN2. Determining which DCAN instance
to use if any at all is done through
CTRL_CORE_CONTROL_SPARE_RW.SEL_ALT_MCAN. Since general pinmuxing is
handled in U-boot. Handle this additional pinmuxing requirement in U-boot
to ensure that MCAN is used by default via the DCAN1 pins.

Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Vignesh R <vigneshr@ti.com>
[fcooper@ti.com: Update commit message and use DCAN1 not DCAN2 for MCAN]
Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>