Replace MAX_ADDR_LEN with its numeric value to fix the following
linux/packet_diag.h userspace compilation error:
/usr/include/linux/packet_diag.h:67:17: error: 'MAX_ADDR_LEN' undeclared here (not in a function)
__u8 pdmc_addr[MAX_ADDR_LEN];
This is not the first case in the UAPI where the numeric value
of MAX_ADDR_LEN is used instead of symbolic one, uapi/linux/if_link.h
already does the same: