Add option to use Ada code in romstage

If selected, libgnat is linked into romstage. In addition, a call to
romstage_adainit() is added to support Ada program data
initialization.

BUG=b:252792591
BRANCH=firmware-brya-14505.B
TEST=Ada code compiles for romstage and loads successfully

Change-Id: I74f0460f6b14fde2b4bd6391e1782b2e5b217707
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70274
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/adainit.h

@@ -15,6 +15,12 @@
  * lizations automatically. When not, we have to call it explicitly.
  */
 
+#if CONFIG(ROMSTAGE_ADA)
+void romstage_adainit(void);
+#else
+static inline void romstage_adainit(void) {}
+#endif
+
 #if CONFIG(RAMSTAGE_ADA)
 void ramstage_adainit(void);
 #else