RISC-V: Add 'H' to canonical extension ordering

This commit adds 'H' to canonical extension ordering based on current
consensus (not officially ratified as a new ISA specification manual
but discussion for software compatibility is made).

bfd/ChangeLog

	* elfxx-riscv.c (riscv_ext_canonical_order): Add 'H' for
	canonical extension ordering based on current consensus.
diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
index a4609b9..ede6968 100644
--- a/bfd/elfxx-riscv.c
+++ b/bfd/elfxx-riscv.c
@@ -1345,7 +1345,7 @@
 }
 
 /* Canonical order for single letter extensions.  */
-static const char riscv_ext_canonical_order[] = "eigmafdqlcbkjtpvn";
+static const char riscv_ext_canonical_order[] = "eigmafdqlcbkjtpvnh";
 
 /* Array is used to compare the orders of standard extensions quickly.  */
 static int riscv_ext_order[26] = {0};