media: flexcop: avoid -Wempty-body warning

Building with 'make W=1' shows many warnings -Wempty-body warnings like

drivers/media/common/b2c2/flexcop-misc.c: In function 'flexcop_determine_revision':
drivers/media/common/b2c2/flexcop-misc.c:35:85: error: suggest braces around empty body in an 'else' statement [-Werror=empty-body]
   35 |                 deb_info("this FlexCop has the 6 basic main hardware pid filter.\n");

drivers/media/usb/b2c2/flexcop-usb.c: In function 'flexcop_usb_process_frame':
drivers/media/usb/b2c2/flexcop-usb.c:357:79: error: suggest braces around empty body in an 'else' statement [-Werror=empty-body]
  357 |                                         deb_ts("not ts packet %*ph\n", 4, b+2);
      |                                                                               ^
drivers/media/common/b2c2/flexcop-misc.c: In function 'flexcop_determine_revision':
drivers/media/common/b2c2/flexcop-misc.c:35:85: error: suggest braces around empty body in an 'else' statement [-Werror=empty-body]
   35 |                 deb_info("this FlexCop has the 6 basic main hardware pid filter.\n");
      |                                                                                     ^

Change the empty dprintk() macros to no_printk(), which avoids this
warning and adds format string checking.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>