Change FPU flags to use single precision FPU (#13)

The Cortex-M33F has a single precision fpu, thus the linker fpu settings need to be set to -mfpu=fpv-sp-d16. Otherwise all calls to the floating point abi will lead to a crash.

builder/frameworks/arduino.py

@@ -142,14 +142,10 @@ def load_flags(filename):
 # Add FPU flags
 #
 
-fpv_version = "4-sp"
-if board.id == "portenta_c33":
-    fpv_version = "5"
-
 env.Append(
     LINKFLAGS=[
         "-mfloat-abi=hard",
-        "-mfpu=fpv%s-d16" % fpv_version
+        "-mfpu=fpv%s-sp-d16" % ("5" if board.id == "portenta_c33" else "4"),
     ]
 )