ggml-hexagon: add hex_supported_buffer for better buffer supported check

[chraac]

Description

This PR introduces a new hex_supported_buffer function to improve buffer support checking in the ggml-hexagon backend.

Changes

• Refactored buffer support checking: Added a dedicated hex_supported_buffer() function to centralize and improve the logic for determining whether a buffer is supported by the Hexagon backend

Benefits

• Better maintainability: Centralized buffer support logic makes the codebase easier to maintain and update
• Improved clarity: The new function provides a clearer and more explicit way to check buffer compatibility
• Reduced duplication: Eliminates redundant buffer checking code throughout the Hexagon backend

[max-krasnyansky]

Very nice!
It was long on my TODO list to rework that part to remove the duplication.
I started with offloading MatMul only and then we added a bunch of Ops but didn't get around to refactoring things.

btw For the supported buffer I was just going to move it into the device_supprots_op() just like other backends do (CUDA, etc) where they just iterate over all valid buffs and check if they are compatible.
This way we won't even need to check buffers in each Op. But there some extra checks needed for repacked buffers.
So might need to keep some in the Ops too. Taking another look ...