uio: Use switch statements when handling UIO_READ vs UIO_WRITE

[jhb]

Summary

This is mostly to reduce the diff with CheriBSD which adds additional
constants to enum uio_rw, but also matches the normal style used for
uio_segflg.

Obtained from: CheriBSD

[jhb]

Drop md.c change

[kib]

sys/amd64/amd64/mem.c

123

Fix style?

sys/arm64/arm64/mem.c

91

same

[jrtc27]

In D45142#1029592, @jhb wrote:

Drop md.c change

How come?

[jhb]

In D45142#1029642, @jrtc27 wrote:

In D45142#1029592, @jhb wrote:

Drop md.c change

How come?

I ended up reworking md.c to check the bio->bp_cmd instead which I think is cleaner. I haven't posted a review for that change yet but will in a bit.

[jhb]

sys/amd64/amd64/mem.c

123

Actually, I think I might fix kernacc to return a bool instead as a followup. The current function is:

int
kernacc(void *addr, int len, int rw)
{
...
	if ((vm_offset_t)addr + len > vm_map_max(kernel_map) ||
	    (vm_offset_t)addr + len < (vm_offset_t)addr)
		return (FALSE);
...
	return (rv == TRUE);
}