can: bcm: bcm_sock_no_ioctlcmd(): mark function as static

This patch marks the bcm_sock_no_ioctlcmd() function as static as it's
only used in this source file.

Fixes: 473d924d ("can: fix ioctl function removal")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>