loader.efi: efipart needs to use ioalign

loader.efi: efipart needs to use ioalign

UEFI specification 2.7A, EFI_BLOCK_IO_PROTOCOL, page 566.

The ioalign property does define the alignment of data buffer.

If the alignment is required and our buffer is not aligned, or if
the data buffer is not multiple of Blocksize, we need to use bounce buffer
to perform the block IO. This is much like with BIOS version, except
there the INT13 needs buffer to be located in low memory.

MFS: r353501
MFC: r347195,350654-350656,351274,351630,351637,352421,352439,352443-352446,352451

Approved by:	re (gjb)