README: Update the submission address to linux-firmware@kernel.org

This new alias will reach all maintainers.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

README

@@ -13,8 +13,7 @@ been permitted to redistribute under separate cover.
 
 To submit firmware to this repository, please send either a git binary
 diff or preferably a git pull request to:
-      David Woodhouse <dwmw2@infradead.org>
-      Ben Hutchings <ben@decadent.org.uk>
+      linux-firmware@kernel.org
 and also cc: to related mailing lists.
 
 Your commit should include an update to the WHENCE file clearly