STM32: enable QSPI test with MX25LM51245G octo SPI

[jeromecoutant]

Summary of changes

ST Octo-SPI was ported on QSPI MBED API,
but no test was exectuted

Basic QSPI test is now available for DISCO-L4R9I (Macronix MX25LM51245G memory)

Impact of changes

target	platform_name	test suite	test case	passed	failed	result	elapsed_time (sec)
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi frequency setting test	1	0	OK	10.37
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi init/free test	1	0	OK	2.01
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi memory id test	1	0	OK	0.11
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi write(1-1-1)/x1 read(1-1-1)/x1 repeat/x1 test	1	0	OK	1.66
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi write(1-1-1)/x1 read(1-1-1)/x1 repeat/x4 test	1	0	OK	3.8
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi write(1-1-1)/x1 read(1-1-1)/x4 repeat/x1 test	1	0	OK	1.64
DISCO_L4R9I-ARMC6	DISCO_L4R9I	tests-mbed_hal-qspi	qspi write(1-1-1)/x4 read(1-1-1)/x1 repeat/x1 test	1	0	OK	2.57

Migration actions required

Documentation

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Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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[ciarmcom]

@jeromecoutant, thank you for your changes.
@ARMmbed/mbed-os-maintainers @ARMmbed/mbed-os-hal @ARMmbed/mbed-os-test @ARMmbed/mbed-os-storage please review.

[kjbracey]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts

[mergify]

This PR does not contain release version label after merging.

[0xc0170]

I've fixed the version: Set to 6.0.0-alpha-2