libopencm3 to config/submodules/ on stm32-vserprog

same as the previous patch, we must no longer use "define"
variables in config/git/ when the path is a subdirectory of
a given project, because it means that the download can only
happen after the main one, and currently if that fails, the
download of the main repo would remain intact, breaking future
builds in ways that we can't control - to be clear, it could
be controlled, but with added code complexity in the build
system, so:

put it in config/submodules/

Signed-off-by: Leah Rowe <leah@libreboot.org>

config/git/stm32-vserprog

@@ -3,12 +3,4 @@
 	loc: stm32-vserprog
 	url: https://codeberg.org/libreboot/stm32-vserprog
 	bkup_url: https://git.disroot.org/libreboot/stm32-vserprog
-	depend: libopencm3
-}
-
-{libopencm3}{
-	rev: 458250dc6147dc807eec9e4d5a6caf38a699ecb1
-	loc: stm32-vserprog/libopencm3
-	url: https://codeberg.org/libreboot/libopencm3
-	bkup_url: https://github.com/libopencm3/libopencm3
 }

config/submodule/stm32-vserprog/libopencm3/module.cfg

@@ -0,0 +1,3 @@
+subrev="458250dc6147dc807eec9e4d5a6caf38a699ecb1"
+subrepo="https://codeberg.org/libreboot/libopencm3"
+subrepo_bkup="https://github.com/libopencm3/libopencm3"

config/submodule/stm32-vserprog/module.list

@@ -0,0 +1 @@
+libopencm3