base-files: install missing /etc/iproute2/ematch_map

This file is needed to properly use the tc ematch modules present in
kmod-sched-core and kmod-sched. It is a read-only index file of ematch
methods used only by tc.
Signed-off-by: Tony Ambardar <itugrok@yahoo.com>

package/base-files/files/etc/iproute2/ematch_map

+# lookup table for ematch kinds
+1	cmp
+2	nbyte
+3	u32
+4	meta
+7	canid
+8	ipset
+9	ipt