efi: payload: bootm: remove redundant reallocations in image loader

The EFI payload loader used to copy OS images, initrds and FDTs into
freshly allocated EFI pages before handing them to LoadImage() or
installing configuration tables. This resulted in unnecessary memory
moves, extra allocations and longer boot times.

Rework the loader to:
  - pass buffers from read_file() or FIT images directly to
    BS->load_image() without intermediate memcpy
  - drop efi_allocate_pages()/efi_free_pages() wrappers where not needed
  - avoid duplicate allocations for initrd and FDT data
  - free only the original buffer after execution/unload

This eliminates redundant reallocations, simplifies the code, and
reduces boot overhead. Boot flow is now more deterministic with fewer
allocation failures possible on memory-constrained systems.

Signed-off-by: Chali Anis <chalianis1@gmail.com>

Author: anischali