Refactor ambient lighting.
Refactor ambient lighting.

Change-Id: Ibfdf4366920c9b0de1b334b91c4acfcae5d94adf
Reviewed-on: https://swiftshader-review.googlesource.com/3791
Reviewed-by: Nicolas Capens <0612353e1fcebbfd4b302d9337447ca0cdfa9122@google.com>
Tested-by: Nicolas Capens <0612353e1fcebbfd4b302d9337447ca0cdfa9122@google.com>

bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,bkaradzic/SwiftShader,google/swiftshader,bkaradzic/SwiftShader,google/swiftshader