x86/mm: Fix some kernel-doc warnings

Fix kernel-doc warnings in arch/x86/mm/ioremap.c and
arch/x86/mm/pageattr.c, just like this one:

  Warning(arch/x86/mm/ioremap.c:204):
     No description found for parameter 'phys_addr'
  Warning(arch/x86/mm/ioremap.c:204):
     Excess function parameter 'offset' description in 'ioremap_nocache'

Signed-off-by: Wanpeng Li <liwp@linux.vnet.ibm.com>
Cc: Gavin Shan <shangw@linux.vnet.ibm.com>
Cc: Wanpeng Li <liwp.linux@gmail.com>
Link: http://lkml.kernel.org/r/1339296652-2935-1-git-send-email-liwp.linux@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>