boards/spark-core: fixed make flash target

boards/spark-core/Makefile.include

@@ -17,7 +17,7 @@ export LINK = $(PREFIX)gcc
 export SIZE = $(PREFIX)size
 export OBJCOPY = $(PREFIX)objcopy
 export TERMPROG = $(RIOTBASE)/dist/tools/pyterm/pyterm
-export FLASHER = $(OBJCOPY) -O binary $(ELFFILE) $(BINFILE) ; dfu-util -d 1d50:607f -a 0 -s 0x08005000:leave -D "$(BINFILE)"
+export FLASHER = dfu-util
 export DEBUGGER = # spark core has no debugger
 export RESET = # dfu-util has no support for resetting the device
 
@@ -30,9 +30,8 @@ export ASFLAGS += -ggdb -g3 $(CPU_USAGE) $(FPU_USAGE) -mlittle-endian
 export LINKFLAGS += -ggdb -g3 -std=gnu99 $(CPU_USAGE) $(FPU_USAGE) -mlittle-endian -static -lgcc -mthumb -mno-thumb-interwork -nostartfiles
 # $(LINKERSCRIPT) is specified in cpu/Makefile.include
 export LINKFLAGS += -T$(LINKERSCRIPT)
-export OFLAGS = -O ihex
-export FFLAGS = $(HEXFILE)
-export DEBUGGER_FLAGS = $(RIOTBOARD)/$(BOARD)/dist/gdb.conf $(ELFFILE)
+export OFLAGS = -O binary
+export FFLAGS = -d 1d50:607f -a 0 -s 0x08005000:leave -D "$(HEXFILE)"
 export TERMFLAGS = -p $(PORT)
 
 # unwanted (CXXUWFLAGS) and extra (CXXEXFLAGS) flags for c++