tests/kms_scaling_modes: New IGT to validate scaling modes

In this IGT, various scaling modes are validated. Scaling
mode is one of the connector properties. This property
defines how a non-native mode is upscaled to the native
mode of an LCD panel.

There are 4 types of scaling modes defined:
	None:
		No upscaling happens, scaling is left to the panel. Not all
		drivers expose this mode.
	Full:
		The output is upscaled to the full resolution of the panel,
		ignoring the aspect ratio. It will expand current image to
		the size of the monitor.
	Center:
		No upscaling happens, the output is centered within the native
		resolution the panel. As a result, black bars may appear
		around the image.
	Full aspect:
		The output is upscaled to maximize either the width or height
		while retaining the aspect ratio. It will fill the screen w/o
		stretching the image. Black bars are placed either on top
		and bottom or left and right of the picture.

v2: -removed test flags/test_cycle_flags() (JP)
    -removed redundant igt_display_commit_atomic() (JP)
    -corrected indentation (JP)
v3: -removed valid_test check, getting covered in
     igt_subtest_with_dynamic() (Bhanu)
    -removed redundant if statement, moved remove_fb()
     before skip (JP)
v4: -Removed unnecessary headers (JP)
    -Corrected usage of igt_dynamic_f() (Bhanu)

Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Bhanuprakash Modem <bhanuprakash.modem@intel.com>