phy: freescale: imx8qm-hsio: Include bitfield.h for FIELD_PREP

In various configurations/architectures, bitfield.h may not be
transitively included, which results in a compiler error because
FIELD_PREP is an unexpanded macro:

  drivers/phy/freescale/phy-fsl-imx8qm-hsio.c:459:8: error: call to undeclared function 'FIELD_PREP'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    459 |         val = FIELD_PREP(HSIO_MODE_MASK, val);
        |               ^
  1 error generated.

Include bitfield.h explicitly to fix the build.

Fixes: 82c56b6d

 ("phy: freescale: imx8qm-hsio: Add i.MX8QM HSIO PHY driver support")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202406170340.7mk3WU3Q-lkp@intel.com/
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240620-phy-fsl-imx8qm-hsio-add-bitfield-include-v1-1-5c7c09ed87e6@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>