irq: rename irq_connect() to IRQ_CONNECT()

It's not a function and requires all its arguments to be build-time
constants. Make this more obvious to the end user to ease confusion.

Change-Id: I64107cf4d9db9f0e853026ce78e477060570fe6f
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>