msm: ramdump: Replace strncpy() and strncat() with a safer alternative

Using snprintf() is safer than the previous implementation since
it leaves room for a NUL character at the end of the destination
string and cannot overflow it.

Change-Id: I6041fecdf9303dcafe741c4520581a1434bb8b01
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>