etnaviv: switch to float_to_ubyte(..)

What does this MR do and why?

etnaviv: switch to float_to_ubyte(..)

The blob generates different values for e.g. this call.

glBlendColor(0.002000f, 0.018000f, 0.030000f, 1.0)

0xff010508, /* [01424] PE.ALPHA_BLEND_COLOR := B=0x8,G=0x5,R=0x1,A=0xff */

etnaviv's etna_cfloat_to_uint8(..) creates different values.

  0.002000: 0x0
  0.018000: 0x4
  0.030000: 0x7

The same applies for the alpha reference value.

Lets drop this hand-rolled conversion helper to get the same values as blob.

Signed-off-by: Christian Gmeiner cgmeiner@igalia.com