coreboot/fam15h: don't build ada toolchain for generic platforms

These folders (fam15h_rdimm and fam15h_udimm) are generic plateforms to gather
patches in common for multiple boards (e.g. kgpe-16 and kcma-d8), this is why we also
disable crossgcc_ada in the configuration, since it will be built by specific boards
if needed, avoiding double compilation.

Signed-off-by: Adrien 'neox' Bourmault <neox@gnu.org>
GNUtoo: split commit
Acked-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
Acked-by: Adrien 'neox' Bourmault <neox@gnu.org>

resources/coreboot/fam15h_rdimm/board.cfg

@@ -6,3 +6,4 @@ payload_grub="n"
 payload_grub_withseabios="n"
 payload_seabios="n"
 payload_memtest="n"
+crossgcc_ada="n"

resources/coreboot/fam15h_udimm/board.cfg

@@ -6,3 +6,4 @@ payload_grub="n"
 payload_grub_withseabios="n"
 payload_seabios="n"
 payload_memtest="n"
+crossgcc_ada="n"