staging: octeon-usb: Replace kmalloc with kmalloc_array

Replace kmalloc with specialized function kmalloc_array
when the size is a multiplication of:
	number_of_elements * size_of_element

Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>