ft2232_spi.c: Pack WREN and op in one ftdi_write_data() call

Every ftdi_write_data() call is quite time consuming as the ftdi-chips
seems to take always 2-3ms to respond.
This leads to what the comment already says: Minimize USB transfers
by packing as many commands as possible together.

So I packed the WREN command together with the following operation
which can be program or erase operation.

This saves about 1 minute when programming a 128MBit Flash with my
config!

See timings WREN in extra ftdi_write_data() call:
https://ibb.co/0c1J25d
WREN packed with op:
https://ibb.co/7G1hLkj

I´m using ftdi-2232H chip. That´s why I put it at this place.
If anyone has a good overview about all programmers:
This could be implemented in spi_write_cmd() in case that it is
compatible to all programmers
or this principle could be transfered to other programmers which act
in a similar way.

Signed-off-by: Simon Buhrow <simon.buhrow@posteo.de>
Change-Id: Ie4a07499ec5ef0af23818593f45dc427285a9e8a
---
M ft2232_spi.c
1 file changed, 18 insertions(+), 11 deletions(-)