err_ptr_deref: re-write the check

err_ptr_deref: re-write the check

Smatch now has a module to handle dereferences (smatch_dereference.c) and
a module to track error pointers (smatch_kernel_err_ptr.c).  These modules
are better than the previous code.  The dereference module handles cross
function dereferences.  The error pointer module is more accurate than the
previous code.  And they result in a much simpler check as well.

This check now has a list of functions which are commonly used without
checking for errors.  That helps cut down on the false positives.

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>