efi_selftest: Update .gitignore

Add the following file to .gitignore
 efi_miniapp_file_image_exception.h

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Use efi_miniapp_*.h instead of file enumeration.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_selftest/.gitignore b/lib/efi_selftest/.gitignore
index 293a17b..5b25169 100644
--- a/lib/efi_selftest/.gitignore
+++ b/lib/efi_selftest/.gitignore
@@ -1,4 +1,3 @@
-efi_miniapp_file_image_exit.h
-efi_miniapp_file_image_return.h
+efi_miniapp_*.h
 *.efi
 *.so