checkpatch: better pattern for inline comments

checkpatch: better pattern for inline comments

checkpatch is unhappy about this line:

    WARNING: Block comments use a leading /* on a separate line
    #50: FILE: hw/acpi/nvdimm.c:1074:
    +                   aml_equal(aml_sizeof(pckg), aml_int(1)) /* 1 element? */));

but there's nothing wrong with it - the check is just too simplistic. It
will also miss lines which mix inline and block comments.

Instead, let's strip all inline comments from a line and then check for block
comments.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>