include/linux/irq*.h: Pad irq structs for KABI

Bugzilla: https://bugzilla.redhat.com/2034264
Depends: https://bugzilla.redhat.com/2024595

Upstream Status: RHEL9 only

Pad irq related structs for KABI.

• The irq_work struct is allocated in some drivers and must be padded.
• irq_desc does not appear to need padding. CONFIG_SPARSE_IRQ=y for all
  arches and irq_desc are allocated via alloc_desc(), which is called in the
  kernel. External modules making function calls act on these allocated
  irq_desc structs.
• struct irq_data is embedded in struct irq_desc and must be padded
• irq_domain structs are included in other structs as pointers. The
  irq_domains are allocated within the kernel, and it is possible to
  allocate additional memory in the irq_domain allocation code. However,
  this code has not changed in RHEL8 and there doesn't appear to be a need
  to make this type of complex change. Instead, repeat what we did in RHEL8
  and add 4 RH_KABI_RESERVE() fields.

To make this commit easier to find in future string searches:
RH_KABI kabi rh_kabi.

Signed-off-by: Prarit Bhargava prarit@redhat.com