efi_loader: make EFI_HAVE_RUNTIME_RESET a user-selectable option

efi_loader: make EFI_HAVE_RUNTIME_RESET a user-selectable option

Expose EFI_HAVE_RUNTIME_RESET as a proper Kconfig boolean with a prompt
so platforms can explicitly enable or disable advertising the EFI reset
runtime service.

The current PSCI-based EFI runtime reset implementation is always
enabled whenever CONFIG_PSCI_RESET is selected, but it does not support
passing the additional arguments required for specialized reset modes.
As a result, reboot requests such as bootloader mode or EDL mode cannot
be propagated correctly and instead fall back to a normal reboot.

By making EFI_HAVE_RUNTIME_RESET user-configurable, platforms that
depend on extended PSCI reset can now explicitly disable EFI runtime
reset handling even when CONFIG_PSCI_RESET is enabled, ensuring
that the kernel retains full control of advanced reboot paths.

Default behavior for existing platforms remains unchanged.

Signed-off-by: Aswin Murugan <aswin.murugan@oss.qualcomm.com>
Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Link: https://patch.msgid.link/20260324175913.92858-2-aswinm@qti.qualcomm.com
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>