can: peak: fix usage of const qualifier in pointers args

Fixes the usage of the const qualifier in the memory pointer arguments
of the declared inline functions. By changing the line containing "const",
this patch also changes the name of the arg into a more usual one.

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>