phy: qcom: add linux/bitfield.h header to fix a build error

Add the <linux/bitfield.h> header to prevent a build error:

drivers/phy/qualcomm/phy-qcom-m31-eusb2.c: In function 'm31eusb2_phy_init':
drivers/phy/qualcomm/phy-qcom-m31-eusb2.c:210:37: error: implicit declaration of function 'FIELD_PREP' [-Wimplicit-function-declaration]
  210 |                                     FIELD_PREP(FSEL, data->fsel));

Fixes: 9c85048 ("phy: qcom: Add M31 based eUSB2 PHY driver")
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Wesley Cheng <[email protected]>
Cc: Melody Olvera <[email protected]>
Cc: Vinod Koul <[email protected]>
Cc: Kishon Vijay Abraham I <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: rddunlap

drivers/phy/qualcomm/phy-qcom-m31-eusb2.c

@@ -3,6 +3,7 @@
  * Copyright (c) 2024-2025 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/err.h>