V4L/DVB: ir-core: fix table resize during keymap init

drivers/media/IR/ir-keytable.c would alloc a suitably sized keymap table
only to have it resized as it is populated with the initial keymap.

Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>