kernel-doc: strip attributes even if they have an argument

An inline function can have an attribute, as in include/linux/log2.h,
and kernel-doc handles this already for simple cases.  However,
some attributes have arguments (e.g. the "target" attribute).
Handle those too.

Furthermore, attributes could be at the beginning of a function
declaration, before the return type.  To correctly handle this case,
you need to strip spaces after the attributes; otherwise, dump_function
is left confused.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>