irqchip/gic-v3-its: Rely on genpool alignment

its_create_device() over-allocated by ITS_ITT_ALIGN - 1 bytes to ensure
that an aligned area was available within the allocation. The new genpool
allocator has its min_alloc_order set to get_order(ITS_ITT_ALIGN) so all
allocations from it should be appropriately aligned.

Remove the over-allocation from its_create_device() and alignment from
its_build_mapd_cmd().

Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Will Deacon <will@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/all/20241002141630.433502-3-steven.price@arm.com

drivers/irqchip/irq-gic-v3-its.c

@@ -706,7 +706,6 @@ static struct its_collection *its_build_mapd_cmd(struct its_node *its,
 	u8 size = ilog2(desc->its_mapd_cmd.dev->nr_ites);
 
 	itt_addr = virt_to_phys(desc->its_mapd_cmd.dev->itt);
-	itt_addr = ALIGN(itt_addr, ITS_ITT_ALIGN);
 
 	its_encode_cmd(cmd, GITS_CMD_MAPD);
 	its_encode_devid(cmd, desc->its_mapd_cmd.dev->device_id);
@@ -3488,7 +3487,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
 	 */
 	nr_ites = max(2, nvecs);
 	sz = nr_ites * (FIELD_GET(GITS_TYPER_ITT_ENTRY_SIZE, its->typer) + 1);
-	sz = max(sz, ITS_ITT_ALIGN) + ITS_ITT_ALIGN - 1;
+	sz = max(sz, ITS_ITT_ALIGN);
 
 	itt = itt_alloc_pool(its->numa_node, sz);