tests/thread_priority_inversion: make Makefile adhere to conventions

tests/thread_priority_inversion/Makefile

-# name of your application
-APPLICATION = thread_priority_inversion
+include ../Makefile.tests_common
 
-# If no BOARD is found in the environment, use this default:
-BOARD ?= native
-
-# This has to be the absolute path to the RIOT base directory:
-RIOTBASE ?= $(CURDIR)/../../
-
-# Comment this out to disable code in RIOT that does safety checking
-# which is not needed in a production environment but helps in the
-# development process:
-CFLAGS += -DDEVELHELP
-
-# Change this to 0 show compiler invocation lines by default:
-QUIET ?= 1
-
-# Modules to include:
 USEMODULE += xtimer
 
 BOARD_INSUFFICIENT_MEMORY := nucleo32-f031