test: input: Fix used uninitialized warning in dix_event_to_core

input.c: In function ‘dix_event_to_core’:
../include/inputstr.h:61:55: warning: ‘*((void *)&ev+80)’ is used uninitialized in this function [-Wuninitialized]
 #define SetBit(ptr, bit)  (((BYTE *) (ptr))[(bit)>>3] |= (1 << ((bit) & 7)))
                                                       ^~

Signed-off-by: Daniel Martin <consume.noise@gmail.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
(cherry picked from commit 0bcc65f2)