spi/bcm63xx: remove unneeded debug message

The spi subsystem already provides this info in a more extensive
debug print except for the nsecs/bit - which wasn't calculated anyway
and fixed to 0.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Acked-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>