ses: don't panic if disk elements have really weird descriptors

SES allows element descriptors to contain characters like spaces and
quotes that devfs does not allow to appear in device aliases. Since SES
element descriptors are outside of the kernel's control, we should
gracefully handle a failure to create a device physical path alias.

PR: 264513
Reported by: Yuri <yuri@aetern.org>
Reviewed by: imp, mav
Sponsored by: Axcient
MFC after: 2 weeks