Samples: Fix compiler warnings in fxload

Samples: Fix compiler warnings in fxload

ezusb.c: In function  "ezusb_cpucs"
ezusb.c:163: warning: initialization discards qualifiers from pointer target type
ezusb.c: At top level:
ezusb.c:193: warning: no previous prototype for "parse_ihex"
ezusb.c:340: warning: no previous prototype for "parse_bin"
ezusb.c:377: warning: no previous prototype for "parse_iic"
ezusb.c: In function "ram_poke":
ezusb.c:451: warning: enumeration value "_undef" not handled in switch
ezusb.c:491: warning: passing argument 2 of "ezusb_write" discards qualifiers from pointer target type