libffi: LoongArch: Fix soft-float builds of libffi

This patch correspond to the upstream PR:
https://github.com/libffi/libffi/pull/817
And has been merged.

libffi/ChangeLog:

	* src/loongarch64/ffi.c: Avoid defining floats
	in struct call_context if the ABI is soft-float.

libffi/src/loongarch64/ffi.c

@@ -58,7 +58,9 @@
 */
 typedef struct call_context
 {
+#if !defined(__loongarch_soft_float)
   ABI_FLOAT fa[8];
+#endif
   size_t a[10];
 } call_context;