OvmfPkg, ArmVirtPkg: clean up SetBootOrderFromQemu() parameter list

OvmfPkg, ArmVirtPkg: clean up SetBootOrderFromQemu() parameter list

With OvmfPkg's original QemuBootOrderLib (and USE_OLD_BDS) gone, we no
longer need the BootOptionList parameter in the SetBootOrderFromQemu()
prototype. Update the library class header file (including the function's
documentation), and adapt the library instance and the call sites.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Gary Ching-Pang Lin <glin@suse.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>