Missing type definition for public_key_t

[marcuschangarm]

Description

When compiling the Mbed Cloud client on a BLE target the GenericSecurityManager fails to compile due to missing type definition for public_key_t.

https://github.com/ARMmbed/mbed-os/blob/master/features/FEATURE_BLE/ble/generic/GenericSecurityManager.h#L344-L362

• Type: Bug
• Priority: Major

[0xc0170]

@donatieng @pan- Please review

[marcuschangarm]

Proposed PR fixes issue.