HV: correct CONFIG_BOARD string of apl up2

The CONFIG_BOARD value in defconfig should match with Makefile, otherwise
the build might be failed in some condition.

Tracked-On: #2291

Signed-off-by: Victor Sun <victor.sun@intel.com>

Author: jsun26intel

hypervisor/arch/x86/configs/apl-up2.config

@@ -1,5 +1,5 @@
 # Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
-CONFIG_BOARD="up2"
+CONFIG_BOARD="apl-up2"
 CONFIG_SERIAL_PCI=y
 CONFIG_SERIAL_PCI_BDF="0:18.0"
 CONFIG_COM_IRQ=6