arm_math.h functions not included in core

@facchinm we have the following code which compiles fine against the nRF52 core (Arduino nRF528x Boards (Mbed OS) v1.1.4), but not against Portenta H7 (M7 core) (Arduino mbed-enabled Boards v1.2.0). I think the CMSIS-DSP functions are not compiled into this core...

```
#include
#include "arm_math.h"

void setup() {
float v1[] = { 3.21f, 1.27f };
float v2[] = { 8.21f, 3.33f };
float dest[2];
arm_add_f32(v1, v2, dest, 2);
Serial.print(dest[0]);
Serial.print(dest[1]);
Serial.println();
}

void loop() {

}
```

This fails when linking with:

```
/var/folders/3r/fds0qzv914ng4t17nhh5xs5c0000gn/T/arduino_build_436493/sketch/asdhjasdhjqwfd2.ino.cpp.o: In function `setup':
/Users/janjongboom/Documents/Arduino/libraries/ei-continuous-gestures-arduino-1.0.10/examples/asdhjasdhjqwfd2/asdhjasdhjqwfd2.ino:30: undefined reference to `arm_add_f32'
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board Arduino Portenta H7 (M7 core).
```