infiniband: Fix up users implicitly relying on getting stat.h

They get it via module.h (via device.h) but we want to clean that up.
When we do, we'll get things like:

  CC [M]  drivers/infiniband/core/sysfs.o
  sysfs.c:361: error: 'S_IRUGO' undeclared here (not in a function)
  sysfs.c:654: error: 'S_IWUSR' undeclared here (not in a function)

so add in the stat header it is using explicitly in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>