V4L/DVB: V4L - vpfe capture - fix for kernel crash

As part of upstream merge, set_params() function was removed from isif.c.
This requires removal of BUG_ON() and check for set_params ptr in
vpfe_capture.c. Without this kernel crash dump is seen while bootup on DM365

Also made following changes:-

 1) converted error messages to debug messages since it is not right to flood
    the console with error messages for user mistakes.
 2) returns -EINVAL if ioctl is not supported

Signed-off-by: Muralidharan Karicheri <m-karicheri2@ti.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>