lib: sbi: Fix sbi_domain_root_add_memregion() for merging memregions

We should decrement root_memregs_count by one after merging two
memregions otherwise new memregion added after a merge will be
appended after last sentinel memregion of zero order.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Xiang W <wxjstz@126.com>

lib/sbi/sbi_domain.c

@@ -521,6 +521,7 @@ int sbi_domain_root_add_memregion(const struct sbi_domain_memregion *reg)
 					nreg1++;
 				}
 				reg_merged = true;
+				root_memregs_count--;
 			}
 		}
 	} while (reg_merged);