Exclude MMCCAM kernels from make universe

They don't provide any value and are quite arbitrary.

Note arm64 GENERIC-MMCCAM was already excluded, just not the NODEBUG
variant.

The option is already build-tested with arm64 LINT kernel.

Reviewed by:	manu
Differential Revision:	https://reviews.freebsd.org/D38458

sys/amd64/conf/GENERIC-MMCCAM

@@ -2,6 +2,8 @@
 # and testing on bhyve
 # $FreeBSD$
 
+#NO_UNIVERSE
+
 include         MINIMAL
 
 ident		GENERIC-MMCCAM

sys/arm/conf/GENERIC-MMCCAM

@@ -5,6 +5,8 @@
 #
 # $FreeBSD$
 
+#NO_UNIVERSE
+
 include		GENERIC
 
 ident		GENERIC-MMCCAM

sys/arm64/conf/GENERIC-MMCCAM-NODEBUG

@@ -7,6 +7,8 @@
 #
 # $FreeBSD$
 
+#NO_UNIVERSE
+
 include GENERIC-MMCCAM
 include "../../conf/std.nodebug"