fdtdec: Cast prior_stage_fdt_address with uintptr_t

At present prior_stage_fdt_address is declared as phys_addr_t. On
a 32-bit platform where phys_addr_t can be 64-bit, assigning its
value to gd->fdt_blob which is a pointer, can cause warnings.

Cast it to uintptr_t before the assignment.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

lib/fdtdec.c

@@ -1572,7 +1572,7 @@ int fdtdec_setup(void)
 		return -1;
 	}
 # elif defined(CONFIG_OF_PRIOR_STAGE)
-	gd->fdt_blob = (void *)prior_stage_fdt_address;
+	gd->fdt_blob = (void *)(uintptr_t)prior_stage_fdt_address;
 # endif
 # ifndef CONFIG_SPL_BUILD
 	/* Allow the early environment to override the fdt address */