Install programs into $(prefix)/bin, not /sbin

At least in many configurations, there is no need to run any
of our programs as root.  Thus, we shouldn't install them in sbin.
diff --git a/openbsc/src/ipaccess/Makefile.am b/openbsc/src/ipaccess/Makefile.am
index 7eb0243..c677b3c 100644
--- a/openbsc/src/ipaccess/Makefile.am
+++ b/openbsc/src/ipaccess/Makefile.am
@@ -2,7 +2,7 @@
 AM_CFLAGS=-Wall $(LIBOSMOCORE_CFLAGS) $(COVERAGE_CFLAGS)
 AM_LDFLAGS = $(LIBOSMOCORE_LIBS) $(COVERAGE_LDFLAGS)
 
-sbin_PROGRAMS = ipaccess-find ipaccess-config ipaccess-proxy
+bin_PROGRAMS = ipaccess-find ipaccess-config ipaccess-proxy
 
 ipaccess_find_SOURCES = ipaccess-find.c