Silence gcc: report_{x, y} are getting initialized.

Silence gcc: report_{x, y} are getting initialized.

Get us rid of:
|   CC     acecad.lo
| acecad.c: In function 'USBReadInput':
| acecad.c:1052:43: warning: 'report_y' may be used uninitialized in this function [-Wuninitialized]
| acecad.c:1052:43: warning: 'report_x' may be used uninitialized in this function [-Wuninitialized]

Both code paths (with XORG_BOTCHED_INPUT or not) will lead report_x and
report_y to be set, but make sure the compiler stops guessing.

Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>
Signed-off-by: Cyril Brulebois <kibi@debian.org>