arch: remove `CONFIG_LEGACY_MULTI_LEVEL_TABLE_GENERATION`

`CONFIG_LEGACY_MULTI_LEVEL_TABLE_GENERATION` had been deprecated since
#66877 for 2 releases, interrupt controller drivers should have been
updated to use the new `IRQ_PARENT_ENTRY_DEFINE()` macro. Remove it.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>