.gitignore: ignore modules.order explicitly

The pattern '*.order' was added by commit c6025f4c ("kbuild: ignore
*.order files") to ignore modules.order files.

I do not see any other user of the '.order' extension.

Ignore 'modules.order' explicitly instead of '*.order'.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

.gitignore

@@ -34,7 +34,6 @@
 *.mod.c
 *.o
 *.o.*
-*.order
 *.patch
 *.s
 *.so
@@ -46,6 +45,7 @@
 *.xz
 Module.symvers
 modules.builtin
+modules.order
 
 #
 # Top-level generic files