[PATCH] config.sub allow arch64c-unknown-freebsd

[Urs Janßen]

config.guess says aarch64c-unknown-freebsd14.0
(cfarm240.cfarm.net, an Arm Morello SoC, quad-core aarch64
Neoverse N1-based CPU implementing CHERI)
but config.sub aarch64c-unknown-freebsd14.0 fails
the fixes it:

--- config.sub.o        2023-08-23 20:39:41.744506000 +0100
+++ config.sub  2023-08-23 20:29:51.576046000 +0100
@@ -1181,7 +1181,7 @@
                case $cpu in
                        1750a | 580 \
                        | a29k \
-                       | aarch64 | aarch64_be \
+                       | aarch64 | aarch64_be | aarch64c \
                        | abacus \
                        | alpha | alphaev[4-8] | alphaev56 | alphaev6[78] \
                        | alpha64 | alpha64ev[4-8] | alpha64ev56 | 
alpha64ev6[78] \