add tinyusb to config/submodule/ for pico-sdk

don't define it as a "depend" variable in config/git/,
because it means putting the files in a subdirectory of
an existing project was was already then downloaded, and
that means it can't be downloaded first; if the download
of it fails, the old download is left intact.

this bug isn't currently fixed in the build system, at all,
so this and other patches are being made to mitigate it.

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

config/git/pico-serprog

@@ -4,12 +4,4 @@
 	url: https://codeberg.org/libreboot/pico-serprog
 	bkup_url: https://git.disroot.org/libreboot/pico-serprog
 	depend: pico-sdk
-	depend: rpi-pico-tinyusb
-}
-
-{rpi-pico-tinyusb}{
-	rev: 86c416d4c0fb38432460b3e11b08b9de76941bf5
-	loc: pico-sdk/lib/tinyusb
-	url: https://codeberg.org/libreboot/tinyusb
-	bkup_url: https://github.com/hathach/tinyusb.git
 }

config/submodule/pico-sdk/module.list

@@ -0,0 +1 @@
+lib/tinyusb

config/submodule/pico-sdk/tinyusb/module.cfg

@@ -0,0 +1,3 @@
+subrev="86c416d4c0fb38432460b3e11b08b9de76941bf5"
+subrepo="https://codeberg.org/libreboot/tinyusb"
+subrepo_bkup="https://github.com/hathach/tinyusb.git"