[Vulkan] Softmax Along Channel Dim (#62239)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62239
Added naive implementation of vulkan softmax (not using shared memory)
Based off of naive implementation of mean, found here:
https://github.com/pytorch/pytorch/blob/2565a33c9812ee4b764b7da1f0ad4a3bd857d811/aten/src/ATen/native/vulkan/glsl/mean.glsl
Test Plan:
After building:
```
build/bin/vulkan_api_test
```
{F637001190}
```
[ RUN ] VulkanAPITest.softmax
[ OK ] VulkanAPITest.softmax (180 ms)
```
Reviewed By: SS-JIA
Differential Revision: D29793150
fbshipit-source-id: 4f9d8e1dae8a43cbcb7063b095fa4726df06c929
