fpga manager: xilinx-spi: remove unneeded, mistyped variables

fpga manager: xilinx-spi: remove unneeded, mistyped variables

Using variables does not add readability here: parameters passed
to udelay*() are obviously in microseconds and their meaning is clear
from the context.

The type is also wrong, udelay expects an unsigned long.

Signed-off-by: Luca Ceresoli <[email protected]>
Signed-off-by: Moritz Fischer <[email protected]>