STM32 EMAC : lock deep sleep

[jeromecoutant]

Description

We avoid target to go into deep sleep when Ethernet is started.

TICKLESS tests are OK with this fix.

target	platform_name	test suite	result	elapsed_time (sec)	copy_method
NUCLEO_F746ZG-ARM	NUCLEO_F746ZG	tests-netsocket-dns	OK	36.9	default
NUCLEO_F746ZG-ARM	NUCLEO_F746ZG	tests-netsocket-tcp	OK	42.68	default
NUCLEO_F746ZG-ARM	NUCLEO_F746ZG	tests-netsocket-udp	OK	22.06	default

Pull request type

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

[0xc0170]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3314
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8219/

Triggering tests

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

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2949
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8219/

[mbed-ci]

Test : SUCCESS

Build number : 3123
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8219/3123