neonvm: add RTC to arm kernel config

[mikhail-sakhnov]

CONFIG_RTC_CLASS to enable RTC subsystem.
CONFIG_RTC_DRV_EFI to use RTC from efi firmware.

With this combination of settings time in guest vm is valid. Otherwise it always starts with 1970- (0 timestamp).

[sharnoff]

Hm, any idea why it's needed on arm and not x86?

[mikhail-sakhnov]

Hm, any idea why it's needed on arm and not x86?

There might be almost infinitive amount of reasons and I haven't invest time into that.
x86 might use CMOS time, or x86 might have some legacy code to handle time without external rtc device.

Plus on arm we use uefi on arm, which might give us different behaviour on such a base level.

I think also the comment in the source code https://github.com/torvalds/linux/blob/master/drivers/rtc/rtc-cmos.c#L10 might be related, specifically the part about x86 bypassing RTC "x86 has code to bypass the RTC framework, directly reading the RTC during boot"

[Omrigan]

See also #712