tinyalsa: avoid install in /usr/local/

Set the PREFIX to avoid installing files in [...]/usr/local/.

Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/tinyalsa/tinyalsa.mk

@@ -16,6 +16,7 @@ endef
 define TINYALSA_INSTALL_STAGING_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) \
 		-C $(@D) \
+		PREFIX="/usr" \
 		CROSS_COMPILE="$(TARGET_CROSS)" \
 		DESTDIR="$(STAGING_DIR)" install
 endef
@@ -23,6 +24,7 @@ endef
 define TINYALSA_INSTALL_TARGET_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) \
 		-C $(@D) \
+		PREFIX="/usr" \
 		CROSS_COMPILE="$(TARGET_CROSS)" \
 		DESTDIR="$(TARGET_DIR)" install
 endef