configurations: Split out ASRock c3.medium/m3.large chassis

Previously the romed8hm3 board config inappropriately included
components from the Open19 c3.medium.x86/m3.large.x86 chassis.  Add a
config for the chassis and move the chassis components from the board
config to it.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Change-Id: I3833bbf810b5e33b409110b867c09e1ca2f45ae2
diff --git a/meson.build b/meson.build
index ab8c4b6..afc59a6 100644
--- a/meson.build
+++ b/meson.build
@@ -78,6 +78,7 @@
     'a2ux8x4riser.json',
     'acbell_rica_psu.json',
     'acbel_r1ca2122a_psu.json',
+    'asrock_c3_medium_x86.json',
     'asrock_e3c246d4i.json',
     'asrock_e3c256d4i.json',
     'asrock_m3_small_x86.json',