media: Convert entity ID allocation to new IDA API

Removes a call to ida_pre_get().

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>