net: pse-pd: tps23881: include missing bitfield.h header

Using FIELD_GET() fails in configurations that don't already include
the header file indirectly:

drivers/net/pse-pd/tps23881.c: In function 'tps23881_i2c_probe':
drivers/net/pse-pd/tps23881.c:755:13: error: implicit declaration of function 'FIELD_GET' [-Wimplicit-function-declaration]
  755 |         if (FIELD_GET(TPS23881_REG_DEVID_MASK, ret) != TPS23881_DEVICE_ID) {
      |             ^~~~~~~~~

Fixes: 89108cb5 ("net: pse-pd: tps23881: Fix the device ID check")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20240807075455.2055224-1-arnd@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/pse-pd/tps23881.c

@@ -5,6 +5,7 @@
  * Copyright (c) 2023 Bootlin, Kory Maincent <kory.maincent@bootlin.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/firmware.h>
 #include <linux/i2c.h>