hv: remove de-privilege boot mode support and remove vboot wrappers

Now ACRN supports direct boot mode, which could be SBL/ABL, or GRUB boot.
Thus the vboot wrapper layer can be removed and the direct boot functions
don't need to be wrapped in direct_boot.c:

- remove call to init_vboot(), and call e820_alloc_memory() directly at the
  time when the trampoline buffer is actually needed.
- Similarly, call CPU_IRQ_ENABLE() instead of the wrapper init_vboot_irq().
- remove get_ap_trampoline_buf(), since the existing function
  get_trampoline_start16_paddr() returns the exact same value.
- merge init_general_vm_boot_info() into init_vm_boot_info().
- remove vm_sw_loader pointer, and call direct_boot_sw_loader() directly.
- move get_rsdp_ptr() from vboot_wrapper.c to multiboot.c, and remove the
  wrapper over two boot modes.

Tracked-On: #5197
Signed-off-by: Zide Chen <zide.chen@intel.com>

hypervisor/boot/include/boot.h

@@ -87,5 +87,6 @@ struct acrn_multiboot_info *get_multiboot_info(void);
 void init_acrn_multiboot_info(void);
 int32_t sanitize_multiboot_info(void);
 void parse_hv_cmdline(void);
+const void* get_rsdp_ptr(void);
 
 #endif /* BOOT_H_ */