riscv: function to retrieve SBI implementation version

Provide function sbi_get_impl_version() to retrieve the SBI implementation
version.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 5030892..bfcd204 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -152,6 +152,7 @@
 void sbi_set_timer(uint64_t stime_value);
 long sbi_get_spec_version(void);
 int sbi_get_impl_id(void);
+int sbi_get_impl_version(long *version);
 int sbi_probe_extension(int ext);
 void sbi_srst_reset(unsigned long type, unsigned long reason);