drm/i915/dg2: Drop 38.4 MHz MPLLB tables

Our early understanding of DG2 was incorrect; since the 5th display
isn't actually a Type-C output, 38.4 MHz input clocks are never used on
this platform and we can drop the corresponding MPLLB tables.

Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220218010328.183423-2-lucas.demarchi@intel.com