FIELD_PREP expects constant arguments. Istead of doing FIELD_PREP
operation on the arguments of combo_phy_w32_off_mask(), pass the
final FIELD_PREP value as an argument.

Error reported as:
In file included from include/linux/build_bug.h:5,
from include/linux/bitfield.h:10,
from drivers/phy/intel/phy-intel-combo.c:8:
drivers/phy/intel/phy-intel-combo.c: In function 'combo_phy_w32_off_mask':
include/linux/bitfield.h:52:28: warning: comparison is always false due to limited range of data type [-Wtype-limits]

include/linux/compiler.h:350:38: error: call to '__compiletime_assert_37' declared with attribute error: FIELD_PREP: mask is not constant
94 |   __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");          |   ^~~~~~~~~~~~~~~~
drivers/phy/intel/phy-intel-combo.c:137:13: note: in expansion of macro 'FIELD_PREP'
137 |  reg_val |= FIELD_PREP(mask, val);
|             ^~~~~~~~~~

../include/linux/compiler.h:392:38: error: call to__compiletime_assert_137
 declared with attribute error:
BUILD_BUG_ON failed: (((mask) + (1ULL << (__builtin_ffsll(mask) - 1))) & (((mask) + (1ULL << (__builtin_ffsll(mask) - 1))) - 1)) != 0
  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)

../include/linux/bitfield.h:94:3: note: in expansion of macro __BF_FIELD_CHECK
   __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
   ^~~~~~~~~~~~~~~~
../drivers/phy/intel/phy-intel-combo.c:137:13: note: in expansion of macro FIELD_PREP
  reg_val |= FIELD_PREP(mask, val);
             ^~~~~~~~~~

Fixes: ac0a95a3 ("phy: intel: Add driver support for ComboPhy")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Dilip Kota <eswara.kota@linux.intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Link: https://lore.kernel.org/r/8a309dd3c238efbaa59d1649704255d6f8b6c9c5.1590575358.git.eswara.kota@linux.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>