ipc: eliminate multiple memcpy() calls

[lyakh]

Eliminate multiple instances of IPC4 data copying, use simple type- casts instead. This removes stack objects and replaces run-time copying with compile-time pointer substitution.

[Copilot]

Pull request overview

This PR reduces IPC4 message handling overhead by removing local stack copies and memcpy_s() calls for several IPC4 request headers, instead interpreting the inbound message via pointer casting and tightening some APIs with const correctness.

Changes:

• Replaces multiple memcpy_s()-to-stack patterns with direct pointer casts for IPC4 request header access in the user IPC4 handler.
• Updates comp_new_ipc4(), ipc4_chain_manager_create(), and ipc4_chain_dma_state() to take const IPC4 request structures.
• Propagates the updated function signatures through relevant public headers.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/ipc/ipc4/helper.c	Makes IPC4 helper entry points accept const request structures (no behavioral change intended).
src/ipc/ipc4/handler-user.c	Removes stack copies / memcpy_s() and switches to direct request-structure pointer access.
src/include/sof/ipc/topology.h	Updates IPC4 chain DMA helper prototypes to match new const signatures.
src/include/sof/audio/component_ext.h	Updates comp_new_ipc4() prototype to accept a const init-instance request.

Suppressed comments (1)

src/ipc/ipc4/handler-user.c:1436

• In CONFIG_LIBRARY builds, config is a pointer here too, so sizeof(config) is the pointer size, not the size of struct ipc4_module_large_config. The payload pointer will be off by 4/8 bytes.

#if CONFIG_LIBRARY
		struct ipc *ipc = ipc_get();
		const char *data = (const char *)ipc->comp_data + sizeof(config);
#else
		const char *data = (const char *)MAILBOX_HOSTBOX_BASE;