ARM: davinci: make irqs.h a local header

The existence of irqs.h in mach-davinci/include/mach only makes sense
without SPARSE_IRQ as it's then expected to define NR_IRQS and is
included from asm/irq.h. As we now support SPARSE_IRQ, this header can
be moved to mach-davinci and used as the source of HW interrupt numbers.

While updating the includes in various files - also rearrange the
headers by directory (linux/asm/mach).

Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>