qca_spi: Fix clock speed for multiple QCA7000

Storing the maximum clock speed in module parameter qcaspi_clkspeed
has the unintended side effect that the first probed instance
defines the value for all other instances. Fix this issue by storing
it in max_speed_hz of the relevant SPI device.

This fix keeps the priority of the speed parameter (module parameter,
device tree property, driver default). Btw this uses the opportunity
to get the rid of the unused member clkspeed.

Fixes: 291ab06e ("net: qualcomm: new Ethernet over SPI driver for QCA7000")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://patch.msgid.link/20241206184643.123399-2-wahrenst@gmx.net


Signed-off-by: Jakub Kicinski <kuba@kernel.org>