drm/i915/jsl: Split EHL/JSL platform info and PCI ids

Recently we came across requirement to identify EHL and JSL
platform to program them differently. Thus Split the basic
platform definition, macros, and PCI IDs to differentiate
between EHL and JSL platforms. Also, IS_ELKHARTLAKE is replaced
with IS_JSL_EHL everywhere.

Changes since V1 :
	- Rebased to avoid merge conflicts
	- Added missed check for jasperlake in intel_uc_fw.c

Cc : Matt Roper <matthew.d.roper@intel.com>
Cc : Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Tejas Upadhyay <tejaskumarx.surendrakumar.upadhyay@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201013192948.63470-1-tejaskumarx.surendrakumar.upadhyay@intel.com