tree/: Convert flashchip write func ptr to enumerate

This forges the way for flashchips.c to be pure declarative
data and lookup functions for dispatch to be pure. This
means that the flashchips data could be extracted out to
be agnostic data of the flashrom code and algorithms.

Squash in,
flashchips.c: convert spi_chip_write_256()
flashchips.c: convert write_jedec_1()
flashchips.c: convert write_jedec()
flashchips.c: convert write_opaque()
flashchips.c: convert spi_chip_write_1()
flashchips.c: convert spi_aai_write()
flashchips.c: convert edi_chip_write()
flashchips.c: convert write_en29lv640b()
flashchips.c: convert write_82802ab()
flashchips.c: convert spi_write_at45db()
flashchips.c: convert write_28sf040()
flashchips.c: convert NULL write

Change-Id: I80149de169464b204fb09f1424a86fc645b740fd
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
---
M flashchips.c
M flashrom.c
M include/flash.h
M sfdp.c
M tests/chip.c
M tests/chip_wp.c
M tests/spi25.c
7 files changed, 684 insertions(+), 599 deletions(-)