Makefile: do not force the release build on install

If we did build any of the other targets, and are just interested
in those and not the release one, we still want to use the 'install'
rule, but not build (and install) the release libraries.

So, remove the dependency on the 'release' target from the 'install'
rule.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

diff -durN am335x-pru-package-506e074859891a2b350eb4f5fcb451c4961410ea.orig/pru_sw/app_loader/interface/Makefile am335x-pru-package-506e074859891a2b350eb4f5fcb451c4961410ea/pru_sw/app_loader/interface/Makefile
--- am335x-pru-package-506e074859891a2b350eb4f5fcb451c4961410ea.orig/pru_sw/app_loader/interface/Makefile	2014-08-18 00:24:36.000000000 +0200
+++ am335x-pru-package-506e074859891a2b350eb4f5fcb451c4961410ea/pru_sw/app_loader/interface/Makefile	2014-10-12 11:39:17.144682697 +0200
@@ -38,7 +38,7 @@
 
 all:	debug release sodebug sorelease
 
-install: release
+install:
 	install -m 0755 -d $(DESTDIR)$(PREFIX)/lib
 	install -m 0755 -d $(DESTDIR)$(PREFIX)/include
 	install -m 0644 $(LIBDIR)/* $(DESTDIR)$(PREFIX)/lib