can: c_can: use proper type for 'instance'

Commit 6439fbce1075 (can: c_can: fix error checking of priv->instance in
probe()) found the warning but applied a suboptimal solution. Since, both
pdev->id and of_alias_get_id() return integers, it makes sense to convert the
variable to an integer and avoid the cast.

Signed-off-by: Wolfram Sang <wsa@sang-engineering.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --cc drivers/net/can/c_can/c_can.h
Simple merge

diff --cc drivers/net/can/c_can/c_can_platform.c
Simple merge