ggml-hexagon: gelu operation (#17921)

ggml-hexagon: gelu operation  (#17921)

* feat: inital support for gelu using sigmoid approximation

* snapshot: faster gelu using polynomial approximation

* test: disable l2-block prefetch in polynomail approximation

* Revert "test: disable l2-block prefetch in polynomail approximation"

This reverts commit 72339994d45b2bed887e79994403c378d90b62b5.

* Revert "snapshot: faster gelu using polynomial approximation"

This reverts commit 2a787a61d11f9e63e5943a2e6d134b2f0c402ace.

* debug: temporarily disable unnecessary log message for debug purpose

* Feat: optiized unaligned sigmoid_f32

* Feat: larger l2prefetch block

* feat: apply unaligned-load optimization on mul and mul_scalar

* Revert "debug: temporarily disable unnecessary log message for debug purpose"

This reverts commit 84f2f23aa9f17e2fa826db969cd825d0ab192995.

* refactor: cleanup commented unused code

* chore: reformat code with clang-formatter to pass cli test

* Revert "chore: reformat code with clang-formatter to pass cli test"

This reverts commit 952877ec24732b12010c7fa7ed3fc8de4b74e718.

* fix: fix loop overflow

* chore: fix formating ci error