at86rf230: Add macro for TRX STATE MASK

Instead of using the 'magic' number of 0x1f the TRX_STATE_MASK macro is
introduced.
Signed-off-by: Christoffer Holmstedt <christoffer.holmstedt@gmail.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/net/ieee802154/at86rf230.c

@@ -292,6 +292,8 @@ struct at86rf230_local {
 #define STATE_BUSY_RX_AACK_NOCLK 0x1E
 #define STATE_TRANSITION_IN_PROGRESS 0x1F
 
+#define TRX_STATE_MASK		(0x1F)
+
 #define AT86RF2XX_NUMREGS 0x3F
 
 static void
@@ -509,7 +511,7 @@ at86rf230_async_state_assert(void *context)
 	struct at86rf230_state_change *ctx = context;
 	struct at86rf230_local *lp = ctx->lp;
 	const u8 *buf = ctx->buf;
-	const u8 trx_state = buf[1] & 0x1f;
+	const u8 trx_state = buf[1] & TRX_STATE_MASK;
 
 	/* Assert state change */
 	if (trx_state != ctx->to_state) {
@@ -667,7 +669,7 @@ at86rf230_async_state_change_start(void *context)
 	struct at86rf230_state_change *ctx = context;
 	struct at86rf230_local *lp = ctx->lp;
 	u8 *buf = ctx->buf;
-	const u8 trx_state = buf[1] & 0x1f;
+	const u8 trx_state = buf[1] & TRX_STATE_MASK;
 	int rc;
 
 	/* Check for "possible" STATE_TRANSITION_IN_PROGRESS */