fpga-manager: altera-ps-spi: use bitrev8x4

Speed up bit reversal by using hardware bit reversal
Add extra code to handle less than 4byte remnants, if any

Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>