part_efi: dcache: allocate cacheline aligned buffers

Currently part_efi.c allocates buffers for the gpt_header, the
legacy_mbr, and the pte (partition table entry) that may be
incorrectly aligned for DMA operations.

This patch uses ALLOC_CACHE_ALIGN_BUFFER for the stack allocated
buffers and memalign to replace the malloc of the pte.

Signed-off-by: Anton Staaf <robotboy@chromium.org>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Albert ARIBAUD <albert.u.boot@aribaud.net>
Acked-by: Mike Frysinger <vapier@gentoo.org>