Fixes cases where functions were not being inlined.

Tests: dEQP-VK.glsl.functions.control_flow.*
Change-Id: Ia752517040f7529ec3b47adc75ec03646d183f6d
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/30214Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>