Add support for Numatolab Neso board.

[bl0x]

Programming SRAM over USB works, when board jumpers are set for JTAG programming mode.

SPI flashing does not work properly (does not boot).
Readback of SPI data yields identical bitstream.

These changes are only tested with hardware revision 2 of the board.

This commit adds:

• a new cable numato-neso.
• a new board neso_a7.

Usage (programming):
openFPGALoader -b neso_a7 top.bit

Usage (flashing):
openFPGALoader -b neso_a7 -f top.bit

Detecting flash works:

openFPGALoader -b neso_a7 -f --detect
empty
write to flash
Jtag frequency : requested 30.00MHz   -> real 30.00MHz  
protect_flash: use: openFPGALoader/spiOverJtag//spiOverJtag_xc7a100tcsg324.bit.gz
load program
Load SRAM: [==================================================] 100.00%
Done
Shift IR 35
ir: 1 isc_done 1 isc_ena 0 init 1 done 1
JEDEC ID: 0x9d6018
Detected: ISSI IS25LP128 256 sectors size: 128Mb
RDSR : 0x00
WIP  : 0
WEL  : 0
BP   : 0
QE   : 0
SRWD : 0

Function Register
RDFR : 01
RES  : 1
TBS  : 0
PSUS : 0
ESUS : 0
IRL  : 0
Done

[trabucayre]

Applied. Thanks @bl0x !
If the flash is correctly updated problems seems related to the flash by itself? Could you try with a bitstream configured in x1? Maybe the chip has its quad enable bit unset.
I haven't this board to test by myself.