ARC: remove #ifdef-ed out include of dead header

There's no (Kconfig) macro CONFIG_BLOCK_DEV_RAM. (CONFIG_BLK_DEV_RAM
does exist though.) But linux/blk.h got killed in 2005 anyway (in a
patch titled "kill blk.h"), so these three lines can be removed.
Signed-off-by: NPaul Bolle <pebolle@tiscali.nl>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

arch/arc/mm/init.c

@@ -10,9 +10,6 @@
 #include <linux/mm.h>
 #include <linux/bootmem.h>
 #include <linux/memblock.h>
-#ifdef CONFIG_BLOCK_DEV_RAM
-#include <linux/blk.h>
-#endif
 #include <linux/swap.h>
 #include <linux/module.h>
 #include <asm/page.h>