forked from Mirrors/opensbi

When only phys_hi is equal to SBI_DBTR_SHMEM_INVALID_ADDR, it may be a legal address. The old code would modify the legal address. Signed-off-by: Xiang W <wxjstz@126.com> Reviewed-by: Himanshu Chauhan <hchauhan@ventanamicro.com>