staging: dgnc: driver.c: removes dgnc_mbuf function

This patch removes the dgnc_mbuf function. This function was causing the
errors:

drivers/staging/dgnc/dgnc_driver.c: In function 'dgnc_mbuf.constprop.0':
drivers/staging/dgnc/dgnc_driver.c:945:1: warning: the frame size of 1032
bytes is larger than 1024 bytes [-Wframe-larger-than=]

drivers/staging/dgnc/dgnc_tty.c: In function 'dgnc_sniff_nowait_nolock':
drivers/staging/dgnc/dgnc_tty.c:614:1: warning: the frame size of 1056
bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch removes it so the kernel won't be making noise when its
device is found on the system.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>