msm: pm-stats: Fix bug in computing size of a string

Use strlen and strcmp instead of sizeof and memcmp to compare strings.
procfs includes the newline character as a part of the buffer. When
using sizeof and memcmp, the newline character is used in the comparison
resulting in unequal bufferes.

Change-Id: Iafce2543596708e28757805cecae1ccec083c691
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>