atm: solos-pci: constify attribute_group structures

Functions working with attribute_groups provided by <linux/sysfs.h>
work with const attribute_group. These attribute_group structures do not
change at runtime so mark them as const.

File size before:
 text      data     bss     dec     hex filename
 35740    28424     832   64996    fde4 drivers/atm/solos-pci.o

File size after:
 text      data     bss     dec     hex filename
 35932    28232     832   64996    fde4 drivers/atm/solos-pci.o

This change was made with the help of Coccinelle.

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>