Add saturation boost feature to SurfaceFlinger

Bug: 62238038
Test: adb shell service call SurfaceFlinger 1022 f 1.5

The saturation boost will be set by framework to increase
the visual appeal of the sRGB mode. It simply modifies the
color transform matrix based on the supplied value (from
0.0 for black and white to 2.0 for 100% extra saturation).

Change-Id: I9832fbe0361acacc8b17300c37c006792c6c1618