can: k61: Changes to support the mpc5746c controller

Add new parameters to account for different MCUs that can
be used with this driver. These devices have different reset
sequences and number of bits per word supported via SPI. Add
bindings for the mpc5746c controller and make the reset signal
optional.

Change-Id: I616dd3cfedf18a6e21683e1c07551c57c62a675d
Signed-off-by: Gustavo Solaira <gustavos@codeaurora.org>