Modify k61 driver to remove support for mpc5746c CAN card

mpc5746c CAN driver will be supported by the unified driver qti-can
also remove rh850 support from qti-can driver.

Change-Id: I6743604c1298b9705ac3550b96c9dae04d5137bd
Signed-off-by: Balachandra C S <balacs@codeaurora.org>