REALTEK_RTL8195AM defines DEVICE_EMAC flag for WiFi driver

[SeppoTakalo]

Description

As explained in porting sections, device should provide EMAC::get_default_instance() only if it is pure Ethernet. Please see:
https://os.mbed.com/docs/v5.9/reference/ethernet-port.html

Also, device should enable EMAC flag in targets.json only if its pure Ethernet. Please see:
https://github.com/ARMmbed/mbed-os/tree/master/features/netsocket/emac-drivers#device_emac

REALTEK_RTL8195AM does both for WiFi interface. It provides EMAC::get_default_instance() and also enables EMAC flag in the device_has section. Both should be removed and #7246 should be fixed by providing default WiFi interface, like this:

#include "RTWInterface.h"

WiFiInterface *WiFiInterface::get_target_default_instance()
{
    static RTWInterface wifi;
    return &wifi;
}

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[ciarmcom]

ARM Internal Ref: MBOTRIAGE-789

[0xc0170]

@ARMmbed/team-realtek Please review

[samchuarm]

@M-ichae-l Hi Michael, please review and address this for RTL8195AM EMAC implementation. Thanks.

[M-ichae-l]

@samchuarm OK. Thank you.

[M-ichae-l]

I have verified the #7259. I will PR (updating the rtl8195am lib and remove the DEVICE_EMAC) soon.

[samchuarm]

Thanks @M-ichae-l Please ref the PR here once you submit it. Thx.

[samchuarm]

Hi @M-ichae-l , any update on the PR?

[M-ichae-l]

@samchuarm
I will PR "remove the DEVICE_EMAC" today. The rtl8195am lib update will together with low power feature in future.

[M-ichae-l]

Please refer to #7551 for the fix.

[samchuarm]

Hi @SeppoTakalo , since #7551 is approved, do you think this issue can be closed now? Thx.