Blackfin: flat: Use %x to format u32

Several variables had their types changed from unsigned long to u32,
but the printk()-style format to print them wasn't updated, leading to:

    arch/blackfin/kernel/flat.c: In function 'bfin_get_addr_from_rp':
    arch/blackfin/kernel/flat.c:35:3: warning: format '%lx' expects argument of type 'long unsigned int', but argument 2 has type 'u32' [-Wformat]
    arch/blackfin/kernel/flat.c: In function 'bfin_put_addr_at_rp':
    arch/blackfin/kernel/flat.c:80:3: warning: format '%lx' expects argument of type 'long unsigned int', but argument 2 has type 'u32' [-Wformat]

Fixes: 468138d7

 ("binfmt_flat: flat_{get,put}_addr_from_rp() should be able to fail")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>