drm/i915/icl: Fix the macros for DFLEXDPMLE register bits

This patch fixes the macros used for defining the DFLEXDPMLE
register bit fields. This accounts for changes in the spec.

Fixes: a2bc69a1 ("drm/i915/icl: Add register definition for DFLEXDPMLE")
Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Jose Roberto de Souza <jose.souza@intel.com>
Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181023191248.26418-1-manasi.d.navare@intel.com