staging/omapdrm: remove the unnecessary initialization of a local variable in omap_crtc.c

The following error fixed.
- ERROR: do not initialise statics to 0 or NULL

Signed-off-by: YAMANE Toshiaki <yamanetoshi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>