hexagon: drop empty and unused free_initrd_mem

hexagon never reserves or initializes initrd and the only mention of it is
the empty free_initrd_mem() function.

As we have a generic implementation of free_initrd_mem(), there is no need
to define an empty stub for the hexagon implementation and it can be
dropped.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Mike Rapoport <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Cc: Richard Kuo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/hexagon/mm/init.c

···
 	init_mm.context.ptbase = __pa(init_mm.pgd);
 }
 
-/*
- * free_initrd_mem - frees...  initrd memory.
- * @start - start of init memory
- * @end - end of init memory
- *
- * Apparently has to be passed the address of the initrd memory.
- *
- * Wrapped by #ifdef CONFIG_BLKDEV_INITRD
- */
-void free_initrd_mem(unsigned long start, unsigned long end)
-{
-}
-
 void sync_icache_dcache(pte_t pte)
 {
 	unsigned long addr;