add lenovo x201 support

note: me6_update_parser needs to be written, similar
to me7_update_parser, to generate the partition
tables within intel me6 on lenovo bios updates.

the current logic in lbmk goes like this:
mkdir -p vendorfiles/cache/

and save your factory dump as:
vendorfiles/cache/x201_factory.rom

the build system has been modified, in such a way
as to support extracting me.bin (which is the full
one) and then neutering from this.

this is done automatically, if the file is present,
but you must first insert that file there, which means
you'll need a dump of the original boot flash on your
thinkpad x201

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

config/vendor/sources

@@ -120,3 +120,9 @@
 	DL_url https://download.lenovo.com/pccbbs/mobiles/g1rg24ww.exe
 	DL_url_bkup https://web.archive.org/web/20210706183911/https://download.lenovo.com/pccbbs/mobiles/g1rg24ww.exe
 }
+
+{x201}{
+	DL_hash x201_factory.rom
+	DL_url rom
+	DL_url_bkup rom
+}