drm/xe: Mark ROW_CHICKEN5 as a masked register

drm/xe: Mark ROW_CHICKEN5 as a masked register

ROW_CHICKEN5 is a masked register (i.e., to adjust the value of any of
the lower 16 bits, the corresponding bit in the upper 16 bits must also
be set).  Add the XE_REG_OPTION_MASKED to its definition; failure to do
so will cause workaround updates of this register to not apply properly.

Bspec: 56853
Fixes: 835cd6cbb0d0 ("drm/xe/xe3p_lpg: Add initial workarounds for graphics version 35.10")
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patch.msgid.link/20260410-xe3p_tuning-v1-3-e206a62ee38f@intel.com
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>