compat: do not include kstrto* for kernel >= 2.6.38.4

compat: do not include kstrto* for kernel >= 2.6.38.4

kstrto* went into kernel 2.6.38.4 and causes conflicts with the version
included in compat-wireless. We use strict_strtol to check if kstrto*
is already available.
kstrto* was not moved to compat-2.6.38.h because kernel version <=
2.6.38.3 needs this backport and some distributions like Ubuntu still
ship an older version of this kernel.

Reported-by: Andreas Hartmann <andihartmann@01019freenet.de>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>