fb: drop two unneeded shadowing variables

fb: drop two unneeded shadowing variables

fbpict.c: In function 'fbGlyphs':
fbpict.c:188:6: warning: declaration of 'x' shadows a previous local
[-Wshadow]
fbpict.c:111:9: warning: shadowed declaration is here [-Wshadow]
fbpict.c:188:9: warning: declaration of 'y' shadows a previous local
[-Wshadow]
fbpict.c:111:12: warning: shadowed declaration is here [-Wshadow]

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Soren Sandmann <ssp@redhat.com>
Reviewed-by: Mark Kettenis <kettenis@openbsd.org>