arch: remove spurious blkdev.h includes

Various files have acquired spurious includes of <linux/blkdev.h> over
time.  Remove them.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-6-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

arch/mips/rb532/prom.c

@@ -16,7 +16,6 @@
 #include <linux/console.h>
 #include <linux/memblock.h>
 #include <linux/ioport.h>
-#include <linux/blkdev.h>
 
 #include <asm/bootinfo.h>
 #include <asm/mach-rc32434/ddr.h>

arch/mips/sibyte/common/cfe.c

@@ -7,7 +7,6 @@
 #include <linux/kernel.h>
 #include <linux/linkage.h>
 #include <linux/mm.h>
-#include <linux/blkdev.h>
 #include <linux/memblock.h>
 #include <linux/pm.h>
 #include <linux/smp.h>

arch/mips/sibyte/swarm/setup.c

@@ -11,7 +11,6 @@
 #include <linux/spinlock.h>
 #include <linux/mm.h>
 #include <linux/memblock.h>
-#include <linux/blkdev.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/screen_info.h>

arch/openrisc/mm/init.c

@@ -25,7 +25,6 @@
 #include <linux/memblock.h>
 #include <linux/init.h>
 #include <linux/delay.h>
-#include <linux/blkdev.h>	/* for initrd_* */
 #include <linux/pagemap.h>
 
 #include <asm/pgalloc.h>