QuarkMin: Use merged variable driver for emulated NV mode

QuarkMin: Use merged variable driver for emulated NV mode

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1323
Merge EmuVariable and Real variable driver.

The real variable driver has been updated to support emulated
variable NV mode and the EmuVariableRuntimeDxe will be removed
later, so use merged variable driver for emulated NV mode.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Kelly Steele <kelly.steele@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Kelly Steele <kelly.steele@intel.com>
Tested-by: Julien Grall <julien.grall@arm.com>
Acked-by: Julien Grall <julien.grall@arm.com>