staging: et131x: Use upper_32_bits() instead of '>> 32'

	'>> 32 of a 32bit value is undefined in C. The compiler is free
	to do what it likes with this...'

Change all uses of '>> 32' to use upper_32_bits() and use
the corresponding lower_32_bits() to match.

Also remove an incorrect comment about dma alloc always returning 32bit
addresses.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>