cam (scsi): silence "Medium not present" SCSI sense logging for removable media

Change SS_FATAL to SS_FAIL for SCSI sense code 0x3A (Medium not present)
to suppress console spam when card readers or other removable media
devices have no media inserted.

The error is still returned to callers (ENXIO), but no longer prints to
dmesg during boot/probe.

Verified with Apple SD Card Reader - reduced boot messages from 4 to 2.

Reviewed by: emaste, imp
Differential Revision: https://reviews.freebsd.org/D55287

(cherry picked from commit 3d218b6289cf4675abdeef17a4489e71f8e1935e)