staging: wfx: simplify virt_addr_valid call

Reviewing sram_write_dma_safe(), there are two
identical calls to virt_addr_valid().  The second
call can be simplified by a comparison of variables
set from the first call.
Reviewed-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20200912144719.13929-1-trix@redhat.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/fwio.c

@@ -94,7 +94,7 @@ static int sram_write_dma_safe(struct wfx_dev *wdev, u32 addr, const u8 *buf,
 		tmp = buf;
 	}
 	ret = sram_buf_write(wdev, addr, tmp, len);
-	if (!virt_addr_valid(buf))
+	if (tmp != buf)
 		kfree(tmp);
 	return ret;
 }