lib: sbi: fix DBTR_SHMEM_MAKE_PHYS for RV64

Obtaining a 64-bit address under rv64 does not require combining
32-bit registers

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
diff --git a/lib/sbi/sbi_dbtr.c b/lib/sbi/sbi_dbtr.c
index 3cc1ef8..94fd049 100644
--- a/lib/sbi/sbi_dbtr.c
+++ b/lib/sbi/sbi_dbtr.c
@@ -48,7 +48,7 @@
 	     _idx++, _entry = ((_etype *)_base + _idx))
 
 #if __riscv_xlen == 64
-#define DBTR_SHMEM_MAKE_PHYS(_p_hi, _p_lo) (((u64)(_p_hi) << 32) | (_p_lo))
+#define DBTR_SHMEM_MAKE_PHYS(_p_hi, _p_lo) (_p_lo)
 #elif __riscv_xlen == 32
 #define DBTR_SHMEM_MAKE_PHYS(_p_hi, _p_lo) (((u64)(_p_hi) << 32) | (_p_lo))
 #else