fdtoverlay: Switch from using alloca to malloc

alloca entails a complicated header situation when using other platforms, where
some split it out in alloca.h while others include it as a standard part of
stdlib.h.

The cons don't seem to outweigh the pros, so switch it to malloc.

Signed-off-by: Kyle Evans <[email protected]>
Signed-off-by: David Gibson <[email protected]>
1 file changed