acpid: fix obvious syntax error in addprefix call

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/acpid/acpid.mk

@@ -26,7 +26,7 @@ endef
 define ACPID_UNINSTALL_TARGET_CMDS
 	rm -f $(TARGET_DIR)/usr/sbin/acpid
 	rm -f $(TARGET_DIR)/usr/bin/acpi_listen
-	rm -f $(addprefix )$(TARGET_DIR)/usr/share/man/man8/,acpid.8 acpi_listen.8)
+	rm -f $(addprefix $(TARGET_DIR)/usr/share/man/man8/,acpid.8 acpi_listen.8)
 endef
 
 define ACPID_CLEAN_CMDS