drivers: can_mcp251xfd: Forward error and remove done label

Currently if initializing one of the registers fails, the return
error gets overwritten by can_set_timing(). Fix by forwarding the
error directly. Also remove unnecessary done label.

Fixes #73586.

Original patch by melvinvdb from #73714.

Signed-off-by: Andriy Gelman <andriy.gelman@gmail.com>