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: 9c8504861c ("phy: qcom: Add M31 based eUSB2 PHY driver")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Wesley Cheng <quic_wcheng@quicinc.com>
Cc: Melody Olvera <melody.olvera@oss.qualcomm.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: Kishon Vijay Abraham I <kishon@kernel.org>
Cc: linux-phy@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Link: https://lore.kernel.org/r/20250617034249.2067135-1-rdunlap@infradead.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

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>