riscv: fpu: switch has_fpu() to riscv_has_extension_likely()

Switch has_fpu() from static branch to the new helper
riscv_has_extension_likely().

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230128172856.3814-7-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/switch_to.h

@@ -59,7 +59,8 @@ static inline void __switch_to_aux(struct task_struct *prev,
 
 static __always_inline bool has_fpu(void)
 {
-	return static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_FPU]);
+	return riscv_has_extension_likely(RISCV_ISA_EXT_f) ||
+		riscv_has_extension_likely(RISCV_ISA_EXT_d);
 }
 #else
 static __always_inline bool has_fpu(void) { return false; }