Don't leak output_info

This inverts the logic to have a more obvious flow for freeing the
output_info.

==26716== 1,161 bytes in 8 blocks are definitely lost in loss record 5 of 7
==26716==    at 0x4A074CD: malloc (vg_replace_malloc.c:236)
==26716==    by 0x395D804ABA: XRRGetOutputInfo (in /usr/lib64/libXrandr.so.2.2.0)
==26716==    by 0x40932B: map_output_xrandr (transform.c:150)
==26716==    by 0x40982F: map_to_output (transform.c:263)
==26716==    by 0x4070A4: main (xinput.c:386)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>