staging: ks7010: Use the ARRAY_SIZE() macro to calculate array sizes.

This macro, provided in 'linux/kernel.h', will calculate the size
more succinctly than a division operation.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>