immediate args to tex ops

nir-to-tgsi emits more compact code than glsl-to-tgsi does, which triggers a virglrenderer bug.

Previously, on dEQP-GLES3.functional.shaders.random.texture.fragment.26 we would get:

FRAG
DCL OUT[0], COLOR
DCL SAMP[0]
DCL SVIEW[0], 2D, FLOAT
DCL TEMP[0], LOCAL
IMM[0] FLT32 {    4.0000,    -5.0000,     0.0000,     0.0000}
  0: MOV TEMP[0].xy, IMM[0].xyyy
  1: MOV TEMP[0].w, IMM[0].zzzz
  2: TXB TEMP[0], TEMP[0], SAMP[0], 2D
  3: MOV OUT[0], TEMP[0]
  4: END
VERT
PROPERTY NEXT_SHADER VERT
DCL IN[0]
DCL OUT[0], POSITION
  0: MOV OUT[0], IN[0]
  1: END
  Pass (Pass)

But now we get:

TGSI after translation from NIR:
FRAG
DCL OUT[0], COLOR
DCL SAMP[0]
IMM[0] UINT32 {1082130432, 3231711232, 0, 0}
  0: TXB OUT[0], IMM[0].xyxz, SAMP[0], 2D
  1: END
  Fail (Image comparison failed)

and virglrenderer fails with:

vtest_client_dispatch_commands: client context created.
GLSL feature level 450
GLSL feature level 450
vrend_compile_shader: context error reported 1 "deqp-gles3" Illegal shader 0
shader failed to compile
0:8(166): error: syntax error, unexpected ';', expecting ')' or ','

fs: 2 GLSL:
   1: #version 140
   2: #extension GL_ARB_shader_bit_encoding : require
   3: 
   4: 
   5:   out  vec4 fsout_c0;
   6: uniform   sampler2D fssamp0;
   7: 
   8: void main(void)
   9: {
  10: fsout_c0 = vec4((texture(fssamp0, uintBitsToFloat(uvec4(1082130432U,3231711232U,1082130432U,0U)).xy, uintBitsToFloat(uvec4(1082130432U,3231711232U,1082130432U,0U))));
  11: }
  12: 

dropping rendering due to missing shaders: deqp-gles3
Mesa: User error: GL_INVALID_VALUE in glDeleteShader
free(): double free detected in tcache 2

(virglrenderer 08e11a49)