package/gcc: remove uclibc-conf patch

package/gcc: remove uclibc-conf patch

This patch is present in Buildroot since a long time and has been rebased on
several version of gcc without beqing upstreamed.  Also it only concern
contrib/regression, which is not used at all during the build...

As suggested by Arnout [1], a test based on qemu_x86_defconfig has
been done without this patch and there is no regression.

[1] http://lists.busybox.net/pipermail/buildroot/2018-May/222104.html

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>