[tests-mbedtls-multi] Fix typo in the printf (no functional change)

[adustm]

Description

testing mbedtls-multi test with verbose option is resulting to OK test, but the display shows differences between awaited result and obtained result.
This is in fact a typo in the printf line showing awaited result.
This PR fixes this.

Pull request type

[ ] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ x ] Test update
[ ] Breaking change

How to reproduce

mbed test -n tests-mbedtls-multi -v

output is :

[1539875137.56][CONN][RXD] received result ctx1 : 248D6A61D20638B8E5C026930C3E6039A33CE45964FF2167F6ECEDD419DB06C1
[1539875137.64][CONN][RXD] awaited result       : 248D6A61D20638B8E5C026930C3E6039A33CE45964FF216F6ECEDD19DB06C1
...
[1539875138.13][CONN][RXD] >>> 'Crypto: sha256_multi': 1 passed, 0 failed
...
mbedgt: test suite 'tests-mbedtls-multi' ............................................................. OK in 16.22 sec
        test case: 'Crypto: sha256_multi' ............................................................ OK in 0.82 sec
        test case: 'Crypto: sha256_split' ............................................................ OK in 0.29 sec

We can see a difference at the end of awaited result compared to received result, but the test is OK
(and it is really ok, I've checked that)

With this PR, the display is now fixed and the awaited result is the correct one.

[1539875137.56][CONN][RXD] received result ctx1 : 248D6A61D20638B8E5C026930C3E6039A33CE45964FF2167F6ECEDD419DB06C1
[1539875137.64][CONN][RXD] awaited result       : 248D6A61D20638B8E5C026930C3E6039A33CE45964FF2167F6ECEDD419DB06C1

[cmonr]

Jeez, that single character diff must've been a pain to find

[NirSonnenschein]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3423
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8482/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 3047
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8482/

[mbed-ci]

Test : SUCCESS

Build number : 3217
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8482/3217