xapp_xinit: point to target's "mcookie"

xapp_xinit: point to target's "mcookie"

The X11 package builds the "mcookie" executable, when selected, into
the directory output/host/usr/bin/mcookie. The xapp_init's "configure"
attempts to find the "mcookie" executable using the host's path. If
the host has an installed "mcookie" application in their /bin folder,
it can influence the build. The following patch forces the expected
mcookie location.

Related:
http://thread.gmane.org/gmane.comp.lib.uclibc.buildroot/50310

Signed-off-by: Yugendra Sai Babu Nadupuru <yugendra.sai.babu.nadupuru@rockwellcollins.com>
Signed-off-by: Matt Weber <matthew.weber@rockwellcollins.com>
[Thomas:
 - remove conditional on the mcookie package being enabled, since
   xapp_xinit depends on the X.org server, and the X.org server
   selects mcookie.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>