selftests/exec: Rename file binfmt_script to binfmt_script.py

Rename file for readability purpose. Update its usage and references.
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/exec/Makefile

@@ -3,7 +3,7 @@ CFLAGS = -Wall
 CFLAGS += -Wno-nonnull
 CFLAGS += -D_GNU_SOURCE
 
-TEST_PROGS := binfmt_script
+TEST_PROGS := binfmt_script.py
 TEST_GEN_PROGS := execveat load_address_4096 load_address_2097152 load_address_16777216 non-regular
 TEST_GEN_FILES := execveat.symlink execveat.denatured script subdir
 # Makefile is a run-time dependency, since it's accessed by the execveat test