Add a comment clarifying the use of pxa3xx_set_datasize() which is only
applicable on data read/write commands (i.e. commands with a data cycle,
such as READID, READ0, STATUS, etc.)
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>