hal-qspi_test: remove STM workaround

[maciejbocianski]

Description

After feature-qspi branch rebase to latest master, everything works fine and workaround is not needed anymore.

@adustm can you confirm that test without workaround works fine on you side

Related PR: #7325

Pull request type

[X] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[cmonr]

/morph build

[adustm]

Hello @maciejbocianski
Thanks for this PR removing the wait.

I've been able to pass the test tests-mbed_hal-qspi on DISCO_L475VG_IOT01A and the result is the same as with the wait.

Kind regards
Armelle

[mbed-ci]

Build : SUCCESS

Build number : 2657
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7580/

Triggering tests

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

[mbed-ci]

Test : SUCCESS

Build number : 2399
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7580/2399

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2291
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7580/