rasdaemon: fix compile against musl libc

rasdaemon: fix compile against musl libc

Fix the following compile errors that occurs when building against musl:

ras-events.c: In function 'read_ras_event_all_cpus':
ras-events.c:366:16: error: 'PATH_MAX' undeclared (first use in this function)
  366 |  char pipe_raw[PATH_MAX];
      |                ^~~~~~~~

ras-events.c: In function 'handle_ras_events_cpu':
ras-events.c:564:16: error: 'PATH_MAX' undeclared (first use in this function)
  564 |  char pipe_raw[PATH_MAX];
      |

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>