qseecom: change the number of bytes to compare app names

keymaster app has two names with different length: "keymaster" and
"keymaste". To compare the app names correctly, the shorter name
length is choosen for memcmp in __qseecom_send_cmd.

Change-Id: I5f0dff7f9756362be40cc64985b65bc2268d734f
Signed-off-by: Zhen Kong <zkong@codeaurora.org>
Signed-off-by: William Clark <wclark@codeaurora.org>