drm/i915/icl: Added 5k source scaling support for Gen11 platform

Gen11 supports upto 5k source scaling

v2: Re-factoring of code as per review
v3: Corrected max Vertical size and indentation
v4: Added max Vertical dst size in same patch

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Nabendu Maiti <nabendu.bikash.maiti@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180323172419.24911-7-paulo.r.zanoni@intel.com