RISC-V: Update testsuite due to -march string relaxation

We has relaxed -march string, it no longer require canonical order, so
we need update some of those testcase.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/arch-23.c: Update test.
	* gcc.target/riscv/arch-27.c: Ditto.
	* gcc.target/riscv/arch-28.c: Ditto.
	* gcc.target/riscv/attribute-10.c: Ditto.

gcc/testsuite/gcc.target/riscv/arch-23.c

@@ -4,7 +4,6 @@ int foo()
 {
 }
 
-/* { dg-error "ISA string is not in canonical order. 'c'" "" { target *-*-* } 0 } */
 /* { dg-error "extension 'w' is unsupported standard single letter extension" "" { target *-*-* } 0 } */
 /* { dg-error "extension 'zvl' starts with 'z' but is unsupported standard extension" "" { target *-*-* } 0 } */
 /* { dg-error "extension 's123' starts with 's' but is unsupported standard supervisor extension" "" { target *-*-* } 0 } */

gcc/testsuite/gcc.target/riscv/arch-27.c

@@ -4,4 +4,4 @@ int foo()
 {
 }
 
-/* { dg-error "ISA string is not in canonical order. 'e'" "" { target *-*-* } 0 } */
+/* { dg-error "'i', 'e' or 'g' must be the first extension" "" { target *-*-* } 0 } */

gcc/testsuite/gcc.target/riscv/arch-28.c

@@ -4,4 +4,4 @@ int foo()
 {
 }
 
-/* { dg-error "ISA string is not in canonical order. 'e'" "" { target *-*-* } 0 } */
+/* { dg-error "'i', 'e' or 'g' must be the first extension" "" { target *-*-* } 0 } */

gcc/testsuite/gcc.target/riscv/attribute-10.c

@@ -3,4 +3,6 @@
 int foo()
 {
 }
-/* { dg-error "unexpected ISA string at end:" "" { target { "riscv*-*-*" } } 0 } */
+/* { dg-error "extension 'u' is unsupported standard single letter extension" "" { target { "riscv*-*-*" } } 0 } */
+/* { dg-error "extension 'n' is unsupported standard single letter extension" "" { target { "riscv*-*-*" } } 0 } */
+/* { dg-error "'i', 'e' or 'g' must be the first extension" "" { target { "riscv*-*-*" } } 0 } */