ihex: add support for CS:IP/EIP records

ihex firmwares can include a jump address for starting execution.  Add a
-j option which will cause this to be written into the generated file as a
record with address zero and data consisting of the address to jump to,
allowing drivers to make use of this information.

This format is chosen because it most closely follows the original ihex
format, though it may make more sense to write a record with length zero
and the address stored as the address.  The records are not omitted by
default since our ihex format does not include record type information and
so including additional records may lead to confusion.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>