crossgcc: fix copy-paste mistake on riscv make target

Change-Id: Id618595a321529770964b125f7490dcb08376643
Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
Reviewed-on: http://review.coreboot.org/8637
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/crossgcc/Makefile

@@ -12,7 +12,7 @@ build-aarch64:
 build-mips:
 	bash ./buildgcc -G -p mips-elf
 
-build-mips:
+build-riscv:
 	bash ./buildgcc -G -p riscv-elf
 
 .PHONY: build-i386-without-gdb