KVM: arm64: Make idregs debugfs iterator search sysreg table directly

KVM: arm64: Make idregs debugfs iterator search sysreg table directly

CTR_EL0 complicates the existing scheme for iterating feature ID
registers, as it is not in the contiguous range that we presently
support. Just search the sysreg table for the Nth feature ID register in
anticipation of this. Yes, the debugfs interface has quadratic time
completixy now. Boo hoo.

Reviewed-by: Sebastian Ott <sebott@redhat.com>
Link: https://lore.kernel.org/r/20240619174036.483943-3-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>