Add empty .scmversion

This overrides the Git-specific part of the kernel version magic. We
previously forced this by setting a (annotated) Git tag but that
requires setting a new tag for each commit.

Change-Id: I44d6dc2bf66fd26b81ce67411b5d380baf4b5ba2
diff --git a/.scmversion b/.scmversion
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/.scmversion