lib: sbi: Only register available extensions

When an extension implements a probe function it means there's a
chance that the extension is not available. Use this function in the
register_extensions callback to determine if the extension should be
registered at all. Where the probe implementation is simple, just
open code the check.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/sbi/sbi_ecall_susp.c

@@ -44,6 +44,12 @@ struct sbi_ecall_extension ecall_susp;
 
 static int sbi_ecall_susp_register_extensions(void)
 {
+	unsigned long out_val;
+
+	sbi_ecall_susp_probe(SBI_EXT_SUSP, &out_val);
+	if (!out_val)
+		return 0;
+
 	return sbi_ecall_register_extension(&ecall_susp);
 }