trivial: Standardise on 32-bit unsigned variables for domain values.

Domains are unnecessarily treated explicitly as 8-bit values within boot info.
Though there are existing proof constraints that limit the maximum domain value
to 8 bits, most of the code would permit domain values up to 32 bits. The
maximum value is unnecessarily constrained in boot info, a restriction which
this commit removes.

Closes VER-341

include/bootinfo.h

@@ -68,7 +68,7 @@ typedef struct bi {
     uint8_t       it_cnode_size_bits; /* initial thread's root CNode size (2^n slots) */
     uint32_t      num_dev_regs;       /* number of device regions */
     bi_dev_reg_t  dev_reg_list[CONFIG_MAX_NUM_BOOTINFO_DEVICE_REGIONS]; /* device regions */
-    uint8_t       it_domain;       /* initial thread's domain ID */
+    dom_t         it_domain;       /* initial thread's domain ID */
 } bi_t;
 
 /* adjust constants in config.h if this assert fails */

libsel4/include/sel4/bootinfo.h

@@ -60,7 +60,7 @@ typedef struct {
     uint8_t           initThreadCNodeSizeBits; /* initial thread's root CNode size (2^n slots) */
     seL4_Word         numDeviceRegions;        /* number of device regions */
     seL4_DeviceRegion deviceRegions[CONFIG_MAX_NUM_BOOTINFO_DEVICE_REGIONS]; /* device regions */
-    uint8_t           initThreadDomain; /* Initial thread's domain ID */
+    uint32_t          initThreadDomain; /* Initial thread's domain ID */
 } seL4_BootInfo;
 
 /* function declarations */

src/kernel/boot.c

@@ -265,7 +265,7 @@ allocate_bi_frame(
     BI_PTR(pptr)->num_iopt_levels = 0;
     BI_PTR(pptr)->ipcbuf_vptr = ipcbuf_vptr;
     BI_PTR(pptr)->it_cnode_size_bits = CONFIG_ROOT_CNODE_SIZE_BITS;
-    BI_PTR(pptr)->it_domain = (uint8_t)ksDomSchedule[ksDomScheduleIdx].domain;
+    BI_PTR(pptr)->it_domain = ksDomSchedule[ksDomScheduleIdx].domain;
 
     return pptr;
 }