net: ieee802154: fix missing checks for regmap_update_bits

regmap_update_bits could fail and deserves a check.

The patch adds the checks and if it fails, returns its error
code upstream.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

drivers/net/ieee802154/mcr20a.c

@@ -533,6 +533,8 @@ mcr20a_start(struct ieee802154_hw *hw)
 	dev_dbg(printdev(lp), "no slotted operation\n");
 	ret = regmap_update_bits(lp->regmap_dar, DAR_PHY_CTRL1,
 				 DAR_PHY_CTRL1_SLOTTED, 0x0);
+	if (ret < 0)
+		return ret;
 
 	/* enable irq */
 	enable_irq(lp->spi->irq);
@@ -540,11 +542,15 @@ mcr20a_start(struct ieee802154_hw *hw)
 	/* Unmask SEQ interrupt */
 	ret = regmap_update_bits(lp->regmap_dar, DAR_PHY_CTRL2,
 				 DAR_PHY_CTRL2_SEQMSK, 0x0);
+	if (ret < 0)
+		return ret;
 
 	/* Start the RX sequence */
 	dev_dbg(printdev(lp), "start the RX sequence\n");
 	ret = regmap_update_bits(lp->regmap_dar, DAR_PHY_CTRL1,
 				 DAR_PHY_CTRL1_XCVSEQ_MASK, MCR20A_XCVSEQ_RX);
+	if (ret < 0)
+		return ret;
 
 	return 0;
 }