qcom: pd-mapper: Null terminate firmware_value string

Null terminate firmware_value string to prevent
strlen() read past the end of buffer.

Otherwise pd-mapper will crash:
  console:/ # pd-mapper
  FORTIFY: strlen: detected read past end of buffer
  Aborted
  134|console:/ #

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Change-Id: Id0b9e1dda2bae12e3a36f1ce40376d1161878894
1 file changed