[nsapi] Fixed iar compilation issue with value initializer

[geky]

Expression needed to init to zero a simple POD struct:

// Before (valid in C99/C++11/G++)
nsapi_addr_t addr = (nsapi_addr_t){}
// After (valid in C++03, invalid in C)
nsapi_addr_t addr = nsapi_addr_t()

cc @sg-, @c1728p9, @bridadan

[bridadan]

/morph test

[c1728p9]

Looks good to me

[mbed-bot]

Result: FAILURE

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 479

A build failure occurred!

[bridadan]

Looks like some targets are too small to fit this code now (that's why there's a build failure).

I'm going to force the tests to run now from that build. I'll come back with the results when they finish.

[geky]

Thanks @bridadan! At the very least it looks like the issue with iar was fixed.