Move KHELP_DECLARE_MOD_UMA later in the boot

Both KHELP_DECLARE_MOD_UMA and the kernel linker SYSINIT to find
in-kernel modules run at SI_SUB_KLD, SI_ORDER_ANY. As the former
depends on the latter running first move it later in the boot,
to the new SI_SUB_KHELP. This ensures KHELP_DECLARE_MOD_UMA
module SYSINIT functions will be after the kernel linker.

Previously we may have received a panic similar to the following if
the order was incorrect:

panic: module_register_init: module named ertt not found

Reported by:	bob prohaska <fbsd AT www.zefox.net>
Discussed with:	imp, jhb
Sponsored by:	The FreeBSD Foundation

sys/sys/kernel.h

@@ -105,6 +105,7 @@ enum sysinit_sub_id {
 	SI_SUB_EVENTHANDLER	= 0x1C00000,	/* eventhandler init */
 	SI_SUB_VNET_PRELINK	= 0x1E00000,	/* vnet init before modules */
 	SI_SUB_KLD		= 0x2000000,	/* KLD and module setup */
+	SI_SUB_KHELP		= 0x2080000,	/* khelp modules */
 	SI_SUB_CPU		= 0x2100000,	/* CPU resource(s)*/
 	SI_SUB_RACCT		= 0x2110000,	/* resource accounting */
 	SI_SUB_KDTRACE		= 0x2140000,	/* Kernel dtrace hooks */

sys/sys/module_khelp.h

@@ -87,7 +87,7 @@ struct khelp_modevent_data {
 		.evhand = khelp_modevent,				\
 		.priv = &kmd_##hname					\
 	};								\
-	DECLARE_MODULE(hname, h_##hname, SI_SUB_KLD, SI_ORDER_ANY);	\
+	DECLARE_MODULE(hname, h_##hname, SI_SUB_KHELP, SI_ORDER_ANY);	\
 	MODULE_VERSION(hname, version)
 
 #define	KHELP_DECLARE_MOD(hname, hdata, hhooks, version)		\