USB: Staging: media: easycap: remove err() usage

err() was a very old USB-specific macro that I thought had
gone away.  This patch removes it from being used in the
driver and uses dev_err() instead.

Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Jesper Juhl <jj@chaosbits.net>
Cc: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>