MFC r298698:
geom: unsign some types to match their definitions and avoid overflows.

In struct:gctl_req, nargs is unsigned.

In mirror:
g_mirror_syncreqs is unsigned.

In raid:
in struct:g_raid_volume, v_disks_count is unsigned.

In virstor:
in struct:g_virstor_softc, n_components is unsigned.

MFC r261084:
malloc() with M_WAITOK doesn't return NULL.

MFC r261085:
Fix typo in r261084.
Add to the gctl_error() an ability to specify error description even
if numeric error code is already specified. Also by default set
error code to EINVAL.

PR: 185852

MFC r261086:
In gctl_copyin() remove unused error variable.
geom_alloc_copyin() can't return ENOMEM, so describe its fail as bad
control request. Add check for NULL pointer in gctl_dump(), since it
can be NULL when geom_alloc_copyin() failed.

MFC r261089:
Remove another unneeded NULL check from geom_alloc_copyin().
Do copyout in case of gctl version mismatch and fix sbuf leak in
g_ctl_ioctl_ctl().

MFC r261091:
Always free sbuf in gctl_free().

MFC r261084:
malloc() with M_WAITOK doesn't return NULL.

MFC r261085:
Fix typo in r261084.
Add to the gctl_error() an ability to specify error description even
if numeric error code is already specified. Also by default set
error code to EINVAL.

PR: 185852

MFC r261086:
In gctl_copyin() remove unused error variable.
geom_alloc_copyin() can't return ENOMEM, so describe its fail as bad
control request. Add check for NULL pointer in gctl_dump(), since it
can be NULL when geom_alloc_copyin() failed.

MFC r261089:
Remove another unneeded NULL check from geom_alloc_copyin().
Do copyout in case of gctl version mismatch and fix sbuf leak in
g_ctl_ioctl_ctl().

MFC r261091:
Always free sbuf in gctl_free().