efi/libstub: Synchronize instruction cache after kernel relocation

efi/libstub: Synchronize instruction cache after kernel relocation

The relocated kernel image is copied to its new location using memcpy().
On architectures with separate instruction and data caches, the copied
instructions may remain stale in the instruction cache, leading to the
execution of outdated contents.

Call efi_cache_sync_image() after the relocation copy to ensure the
instruction cache is synchronized with the updated memory contents before
control is transferred to the relocated kernel.

Signed-off-by: WANG Rui <r@hev.cc>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>