x86: rtc: Drop PNP device check

x86: rtc: Drop PNP device check

Previous changes effectively prevented PNP devices from being created
for the CMOS RTC on x86 with ACPI.

Although in principle a CMOS RTC PNP device may exist on an x86 system
without ACPI (that is, an x86 system where there is no ACPI at all, not
one booted with ACPI disabled), such systems were there in the field ~30
years ago and most likely they would not be able to run a contemporary
Linux kernel.

For the above reasons, drop the PNP device check from add_rtc_cmos().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com> # x86
Link: https://patch.msgid.link/8660687.T7Z3S40VBb@rafael.j.wysocki