libc/riscv64: implement bcopy() and bzero() through memcpy() and memset()

This picks up the accelerated string functions written by
strajabot@.

Event:		Google Summer of Code 2024
MFC after:	1 month
MFC to:		stable/15
See also:	79e01e7e64
Approved by:	markj (mentor)
Differential Revision:	https://reviews.freebsd.org/D53248

lib/libc/riscv/string/Makefile.inc

@@ -1,4 +1,6 @@
 MDSRCS+= \
+	bcopy.c \
+	bzero.c \
 	memchr.S \
 	memcpy.S \
 	memset.S \

lib/libc/riscv/string/bcopy.c

@@ -0,0 +1,14 @@
+/*-
+ * Public domain.
+ */
+
+#include <string.h>
+
+#undef bcopy	/* _FORTIFY_SOURCE */
+
+void
+bcopy(const void *src, void *dst, size_t len)
+{
+
+	memmove(dst, src, len);
+}

lib/libc/riscv/string/bzero.c

@@ -0,0 +1,14 @@
+/*-
+ * Public domain.
+ */
+
+#include <string.h>
+
+#undef bzero	/* _FORTIFY_SOURCE */
+
+void
+bzero(void *b, size_t len)
+{
+
+	memset(b, 0, len);
+}