config: optional extension check for inputproto not required

config: optional extension check for inputproto not required

The check should be in PKG_CHECK_MODULES permanently.

The XORG_DRIVER_CHECK_EXT will add inputproto to PKG_CHECK_MODULES
only if the extension is available. By definition, this extension
is always available and the acecad driver cannot function without it.

This is evidenced by the absence of XINPUT conditional code.

Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Gaetan Nadon <memsize@videotron.ca>