MAKEALL: remove obsolete at91rm9200 soc

Since complete at91rm9200 SoC device was droped (due to replacement with
common at91 code) this parameter can safely be removed.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>

MAKEALL

@@ -444,7 +444,6 @@ LIST_ARMV7="		\
 #########################################################################
 
 LIST_at91="$(boards_by_soc at91)\
-	$(boards_by_soc at91rm9200)\
 	at91sam9260ek		\
 	at91sam9261ek		\
 	at91sam9263ek		\