RISC-V: Fix testcase after bump isa spec version

Extension version might be different among different ISA spec version,
add explicitly isa-spec version to prevent that might fail when build
GCC with different default ISA version.

gcc/testsuite/ChangeLog

	* gcc.target/riscv/attribute-19.c: Add -misa-spec=2.2

gcc/testsuite/gcc.target/riscv/attribute-19.c

@@ -1,4 +1,4 @@
 /* { dg-do compile } */
-/* { dg-options "-mriscv-attribute -march=rv64imp0p9 -mabi=lp64" } */
+/* { dg-options "-mriscv-attribute -march=rv64imp0p9 -mabi=lp64 -misa-spec=2.2" } */
 int foo() {}
 /* { dg-final { scan-assembler ".attribute arch, \"rv64i2p0_m2p0_p0p9\"" } } */