vulkan: optimize iq1 coopmat2 dequant functions

[jeffbolznv]

Perf on RTX 4070:

before:
  MUL_MAT(type_a=iq1_s,type_b=f32,m=4096,n=512,k=14336,bs=[1,1],nr=[1,1],per=[0,1,2,3]):                 460 runs -  2174.26 us/run -  60.13 GFLOP/run -  27.66 TFLOPS
  MUL_MAT(type_a=iq1_m,type_b=f32,m=4096,n=512,k=14336,bs=[1,1],nr=[1,1],per=[0,1,2,3]):                 288 runs -  3482.95 us/run -  60.13 GFLOP/run -  17.26 TFLOPS
  
after:
  MUL_MAT(type_a=iq1_s,type_b=f32,m=4096,n=512,k=14336,bs=[1,1],nr=[1,1],per=[0,1,2,3]):                 726 runs -  1379.33 us/run -  60.13 GFLOP/run -  43.59 TFLOPS
  MUL_MAT(type_a=iq1_m,type_b=f32,m=4096,n=512,k=14336,bs=[1,1],nr=[1,1],per=[0,1,2,3]):                 412 runs -  2428.05 us/run -  60.13 GFLOP/run -  24.76 TFLOPS

[0cc4m]

Master:

model	size	params	backend	ngl	test	t/s
llama 8B IQ1_S - 1.5625 bpw	1.87 GiB	8.03 B	Vulkan	99	pp512	2609.84 ± 16.94
llama 8B IQ1_S - 1.5625 bpw	1.87 GiB	8.03 B	Vulkan	99	tg128	65.52 ± 0.36

PR:

model	size	params	backend	ngl	test	t/s
llama 8B IQ1_S - 1.5625 bpw	1.87 GiB	8.03 B	Vulkan	99	pp512	3461.18 ± 47.70
llama 8B IQ1_S - 1.5625 bpw	1.87 GiB	8.03 B	Vulkan	99	tg128	66.59 ± 1.57