ia64: make num_rsvd_regions static

Commit f6280099

 ("ia64: switch to NO_BOOTMEM") removed the last
user of num_rsvd_regions outside arch/ia64/kernel/setup.c.

Link: https://lkml.kernel.org/r/a377b5437e3e9da93d02f996fe06a2b956cb0990.1629884459.git.geert+renesas@glider.be
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Jay Lan <jlan@sgi.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Simon Horman <horms@verge.net.au>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>