NR_MAX_IRQS is defined as 272 and IRQ_INVALID as 273 which implies
that 272 is a valid irq number. In this case, an illegal access can
occur at run time when irq_desc_array[] or irq_count[] is accessed
with index 272. This fix stops the illegal access by renaming
NR_MAX_IRQS to NR_IRQS and then places proper conditions for range
checks. If the index is >= NR_IRQS, then index is invalid otherwise
its considered valid for accessing irq arrays. IRQ_INVALID definition
is also changed to 0xffffffffU to indicate maximum unsigned value.
Signed-off-by: Madeeha Javed <madeeha_javed@mentor.com>