acpi/cstate: Make sure we could handle C-state deeper than C3

acpi/cstate: Allow request deeper C-state, even it has no _CST entry

On laptop, BIOS may unveil more C-states if power cable is unplugged,
which means if you want to use these deeper C-states you wi

acpi/cstate: Allow request deeper C-state, even it has no _CST entry

On laptop, BIOS may unveil more C-states if power cable is unplugged,
which means if you want to use these deeper C-states you will have to
re-adjust C-state sysctls. This commit automates this kind of
"re-adjust". Read-only sysctl nodes hw.acpi.cpuX.cx_lowest_use and
hw.acpi.cpu.cx_lowest_use are introduced to show the current deepest
C-state could be used.

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cputimer/intr: Restart only if the intr cputimer is changed

kernel: Use DEVMETHOD_END in the drivers.

kernel: Move sys/dev/acpica5 to sys/dev/acpica.

The 5 used to indicate that it was imported from FreeBSD 5 but that
doesn't matter anymore.

In-discussion-with: sephe