hv: Makefile: Separate x86 and common makefile

Currently ACRN supports only x86 architecture. And this patch is the
first of a series of patches to enable ACRN on multiple architecture.

This commit does the multi-arch of Makefile: put x86 specific content
into arch/x86/Makefile.

This includes:
- Pre-launched VM ACPI binary generation
- acrn.32.out generation (32 bit ELF was generated towards i386
  architecture)
- Customized modularization (*_MOD). Only one module is created in
  common section: COMMON_MOD
- Architecture specific make targets and pre-build actions are moved to
  architecture specific makefile. Introduce the following variable to
  register arch targets and/or actions:
  - ARCH_PRE_BUILD_TARGETS
  - ARCH_ALL_TARGETS
  - ARCH_INSTALL_TARGETS

Tracked-On: #8782
Signed-off-by: Yifan Liu <[email protected]>
Acked-by: Wang, Yu1 <[email protected]>

Author: yfliuuu