spi-mem and gpio chipselects

[Chris Packham]

Hi,

I'm working on a platform that has a slightly complicated scheme for
SPI chip-selects using gpios[1]. The spi controller driver in this case
supports the spi-mem operations which appear to bypass the generic
spi_set_cs().

Would there be any harm in adding calls to spi_set_cs() to spi-mem.c?
Naively spi_mem_access_start() and spi_mem_access_end() seem like
convenient places to start.

--
[1] - similar design to 
https://marc.info/?l=linux-spi&m=155504537628635&w=2 but a different
platform.