staging: rtl8712: simplify evm_db2percentage()

Use clamp() to simplify function evm_db2percentage() and reduce object
file size.
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20200118195305.16685-3-straube.linux@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/rtl8712_recv.c

@@ -663,17 +663,11 @@ static u8 evm_db2percentage(s8 value)
 	/*
 	 * -33dB~0dB to 0%~99%
 	 */
-	s8 ret_val;
+	s8 ret_val = clamp(-value, 0, 33) * 3;
 
-	ret_val = value;
-	if (ret_val >= 0)
-		ret_val = 0;
-	if (ret_val <= -33)
-		ret_val = -33;
-	ret_val = -ret_val;
-	ret_val *= 3;
 	if (ret_val == 99)
 		ret_val = 100;
+
 	return ret_val;
 }