Some drivers could do with using records like Intel HEX, but with each
record being larger than 256 bytes. This has been possible in the binary
representation (struct ihex_binrec) in the kernel since the beginning --
at least of the the current version of history. But we haven't been able
to represent that in the .HEX files which get converted to .fw files.

This adds a '-w' option to ihex2fw to make it interpret the first _two_
bytes of each line as the record length, instead of only one byte. And
adds makefile rules for %.H16->%.fw which use that.
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

Not the straight conversion to binary which objcopy can do for us, but
actually representing each record with its original {addr, length},
because some drivers need that information preserved.

Fix up 'firmware_install' to be able to build $(hostprogs-y) too.
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>