SSR: Make smem ramdump devices unique

If two SSR drivers register with the same ramdump device pointing
at shared memory sysfs will complain about duplicate sysfs nodes:

WARNING: at fs/sysfs/dir.c:455 sysfs_add_one+0x78/0x98()
sysfs: cannot create duplicate filename
'/devices/virtual/misc/ramdump_smem'

Avoid this case by making the names of the ramdump devices
unique via smem-$subsystem (smem-modem, smem-dsps, etc.).

Change-Id: I6c3d5b0a4a7739a42b14940a141cc0c87168a4e0
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>