The convert_float_int was not scaling the [0,1] value to the full
1.31 fixed-point range before clamping the value.

Fixes all failures in:
dEQP-GLES3.functional.state_query.floats*

Change-Id: Ic558eb45f1f351d3c30a0a5047a1b252edb56bd0
Reviewed-on: https://swiftshader-review.googlesource.com/14968Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>