riscv mcontext_t/sigcontext: use __aligned__ instead of aligned

aligned may be defined by the application for its own use before
bits/signal.h is included.

arch/riscv32/bits/signal.h

@@ -19,7 +19,7 @@ struct __riscv_mc_d_ext_state {
 };
 
 struct __riscv_mc_q_ext_state {
-	unsigned long long __f[64] __attribute__((aligned(16)));
+	unsigned long long __f[64] __attribute__((__aligned__(16)));
 	unsigned int __fcsr;
 	unsigned int __reserved[3];
 };

arch/riscv64/bits/signal.h

@@ -19,7 +19,7 @@ struct __riscv_mc_d_ext_state {
 };
 
 struct __riscv_mc_q_ext_state {
-	unsigned long long __f[64] __attribute__((aligned(16)));
+	unsigned long long __f[64] __attribute__((__aligned__(16)));
 	unsigned int __fcsr;
 	unsigned int __reserved[3];
 };