sysfs: Fixes __BIN_ATTR_WO() macro

This patch fixes the size and write parameter for the macro
__BIN_ATTR_WO().

Fixes: 7f905761 ("sysfs: add BIN_ATTR_WO() macro")
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1569973038-2710-1-git-send-email-nayna@linux.ibm.com