lib: sbi_domain: Introduce domain intialization order

Currently, the domain initialization order is implied by the order
in which domains are populated by sbi_platform_domains_init() from
sbi_domain_finalize(). This is not documented anywhere and forces
unecessary ordering between domain DT nodes.

To address the above, introduce per-domain 32-bit integer to represent
intialization order (aka "init_order") where domain with a lower
initialization order will be booted first and two domains must not
have same initialization order. For DT based domain creation, new
"init-order" DT property can be used in domain DT node to specify
the initialization order. The ROOT domain is assumed to have lowest
initialization order (aka 0xffffffff).

Signed-off-by: Anup Patel <anup.patel@oss.qualcomm.com>
Reviewed-by: Pawandeep Oza <pawandeep.oza@oss.qualcomm.com>
Tested-by: Pawandeep Oza <pawandeep.oza@oss.qualcomm.com>
Reviewed-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
Link: https://lore.kernel.org/r/20260905131748.922920-4-anup.patel@oss.qualcomm.com
Signed-off-by: Anup Patel <anup@brainfault.org>

include/sbi/sbi_domain.h

@@ -199,6 +199,8 @@ struct sbi_domain {
 	spinlock_t assigned_harts_lock;
 	/** Name of this domain */
 	char name[64];
+	/** Initialization order of this domain */
+	u32 init_order;
 	/** Possible HARTs in this domain */
 	const struct sbi_hartmask *possible_harts;
 	/** Array of memory regions terminated by a region with order zero */