Don't hardcode grouping data into 4-byte words in print_hex_dump()
implementation and instead pass 'groupsize' to memory_display(), since
that's what that parameter is for.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>