genericx86: disable rootless X

Not all video drivers support rootless X and this BSP aims to have broader
support than atom-pc.

(From meta-yocto rev: ea900a29a7cc28dc2bb568bd9d6f91efc326a814)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-yocto-bsp/conf/machine/genericx86.conf

@@ -36,5 +36,3 @@ APPEND += "usbcore.autosuspend=1"
 GLIBC_ADDONS = "nptl"
 
 EXTRA_OECONF_append_pn-matchbox-panel-2 = " --with-battery=acpi"
-
-ROOTLESS_X = "1"