KVM: arm64: selftests: Determine effective counter width in arch_timer_edge_cases

arch_timer_edge_cases uses ~0 as the maximum counter value, however there's
no architectural guarantee that this is valid.

Figure out the effective counter width based on the effective frequency
like it's done by the kernel.

This also serves as a workaround for AC03_CPU_14 that led to the
following assertion failure on ampere-one machines:

==== Test Assertion Failure ====
  arm64/arch_timer_edge_cases.c:169: timer_condition == istatus
  pid=11236 tid=11236 errno=4 - Interrupted system call
     1  0x0000000000404ce7: test_run at arch_timer_edge_cases.c:938
     2  0x0000000000401ebb: main at arch_timer_edge_cases.c:1053
     3  0x0000ffff9fa8625b: ?? ??:0
     4  0x0000ffff9fa8633b: ?? ??:0
     5  0x0000000000401fef: _start at ??:?
  0x1 != 0x0 (timer_condition != istatus)

Note that the following subtest only worked since the counter initialized
with CVAL_MAX would instantly overflow (which is no longer the case):

	test_set_cnt_after_cval_no_irq(timer, 0, DEF_CNT, CVAL_MAX, sm);

To fix this we could swap CVAL_MAX for 0 here but since that is already
done by test_move_counters_behind_timers() let's remove that subtest.

Link: https://lore.kernel.org/kvmarm/ac1de1d2-ef2b-d439-dc48-8615e121b07b@redhat.com
Link: https://amperecomputing.com/assets/AmpereOne_Developer_ER_v0_80_20240823_28945022f4.pdf
Signed-off-by: Sebastian Ott <sebott@redhat.com>
Link: https://lore.kernel.org/r/20250605103613.14544-5-sebott@redhat.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

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