tile: avoid defining INT_MASK macro in <arch/interrupts.h>

Unfortunately, this name conflicts with a different use of
the name in various places through the tree, so don't provide
it for the kernel.  We preserve it for userspace to avoid
breaking any userspace code that relies on this definition.

This fixes a number of compile errors for various drivers that
are enabled by "allyesconfig".

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>