package/moarvm: fix libffi select

moarvm's dyncall supports powerpc64 since version 2020.05 and
https://github.com/MoarVM/MoarVM/commit/d2e84186764bd3c45e7e10547f87ffc5a06f9efd

moarvm's dyncall supports mips since version 2020.02 and
https://github.com/MoarVM/MoarVM/commit/657b536cf6e861ac0bb4bf550e8aea5042a950be

dyncall does not support RISC-V as stated in https://dyncall.org/index

Fixes:
 - http://autobuild.buildroot.org/results/027b7d15e6a6111409ed17bb29e001b6c6d9e0cf

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/moarvm/Config.in

@@ -8,10 +8,8 @@ config BR2_PACKAGE_MOARVM
 	select BR2_PACKAGE_LIBUV
 	select BR2_PACKAGE_LIBTOMMATH
 	select BR2_PACKAGE_LIBATOMIC_OPS
-	# dyncall does not work on MIPS; libffi needs to be used.
-	# See: https://github.com/MoarVM/MoarVM/issues/222
-	# dyncall does not work also on powerpc64 and powerpc64le
-	select BR2_PACKAGE_LIBFFI if BR2_mips || BR2_mipsel || BR2_mips64 || BR2_mips64el || BR2_powerpc64 || BR2_powerpc64le
+	# dyncall does not work on riscv
+	select BR2_PACKAGE_LIBFFI if BR2_riscv
 	select BR2_PACKAGE_ZSTD
 	help
 	  Short for "Metamodel On A Runtime", MoarVM is a virtual