configurations: Add ASRock SPC621D8HM3 board

This is a half-width, AST2500-based, single-socket Xeon server board
employed in the ASRock n3.xlarge.x86 server.

Tested: All motherboard-based sensors work as expected in an ASRock
n3.xlarge.x86 server.

Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Change-Id: If1bacace1637761ddabbc0e2daf6803d4475e0f0
diff --git a/meson.build b/meson.build
index c8112de..e42a4e4 100644
--- a/meson.build
+++ b/meson.build
@@ -81,6 +81,7 @@
     'acbel_r1ca2122a_psu.json',
     'asrock_e3c246d4i.json',
     'asrock_romed8hm3.json',
+    'asrock_spc621d8hm3.json',
     'bletchley_baseboard.json',
     'bletchley_chassis.json',
     'bletchley_frontpanel.json',