unix/linux: adjust comment regarding riscv64 support

The riscv64 port is supported since Go 1.14, adjust the comment in
mkall.go accordingly.

Change-Id: I4b3f218abe9c864c855e89f132e67e9d86754a53
Reviewed-on: https://go-review.googlesource.com/c/sys/+/288333
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/linux/mkall.go b/unix/linux/mkall.go
index 69825db..f1686ac 100644
--- a/unix/linux/mkall.go
+++ b/unix/linux/mkall.go
@@ -52,9 +52,9 @@
 	Bits       int
 }
 
-// List of all Linux targets supported by the go compiler. Currently, riscv64
-// and sparc64 are not fully supported, but there is enough support already to
-// generate Go type and error definitions.
+// List of all Linux targets supported by the go compiler. Currently, sparc64 is
+// not fully supported, but there is enough support already to generate Go type
+// and error definitions.
 var targets = []target{
 	{
 		GoArch:    "386",