elf: Add support for PPC64 ELF V1 ABI in bootelf

elf: Add support for PPC64 ELF V1 ABI in bootelf

This update adds PPC64 ELF V1 ABI support to bootelf for both the
program header and section header options. Elf64 support was already
present for the program header option, but it was not handling the
PPC64 ELF V1 ABI case. For the PPC64 ELF V1 ABI, the e_entry field of
the elf header must be treated as function descriptor pointer instead
of a function address. The first doubleword of the function descriptor
is the function's entry address.

Signed-off-by: Rob Bracero <robbracero@gmail.com>
[trini: Fix whitespace issues]
Signed-off-by: Tom Rini <trini@konsulko.com>