riscv: Introduce Vector enable/disable helpers

These are small and likely to be frequently called so implement as
inline routines (vs. function call).

Co-developed-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230605110724.21391-8-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/vector.h

@@ -11,12 +11,23 @@
 #ifdef CONFIG_RISCV_ISA_V
 
 #include <asm/hwcap.h>
+#include <asm/csr.h>
 
 static __always_inline bool has_vector(void)
 {
 	return riscv_has_extension_unlikely(RISCV_ISA_EXT_v);
 }
 
+static __always_inline void riscv_v_enable(void)
+{
+	csr_set(CSR_SSTATUS, SR_VS);
+}
+
+static __always_inline void riscv_v_disable(void)
+{
+	csr_clear(CSR_SSTATUS, SR_VS);
+}
+
 #else /* ! CONFIG_RISCV_ISA_V  */
 
 static __always_inline bool has_vector(void) { return false; }