accel/amdxdna: Create shared functions for AIE2 and AIE4

accel/amdxdna: Create shared functions for AIE2 and AIE4

The AIE4 platform uses a mailbox management channel mechanism similar to
AIE2 to communicate with the firmware.

Create aie.h and aie.c and move the functions and structures that can
be shared by both platforms from the AIE2-specific files into these
common files. This allows AIE2 and AIE4 to reuse the same implementation
and reduces code duplication.

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260330163705.3153647-2-lizhi.hou@amd.com