package/fft-eval: drop unused variable

Commit 21d5d592a427 (package/fft_eval: new package) got last-minute
changes when comitted, changes which no longer made use of the
FFT_EVAL_TARGETS variable, but forgot to drop assignments to that
variable.

Drop them now.

Reported-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/fft-eval/fft-eval.mk

@@ -13,12 +13,10 @@ FFT_EVAL_LICENSE_FILES = \
 	LICENSES/OFL-1.1.txt
 
 FFT_EVAL_CONV_OPTS = CONFIG_fft_eval_json=y
-FFT_EVAL_TARGETS = fft_eval_json
 
 ifeq ($(BR2_PACKAGE_SDL2)$(BR2_PACKAGE_SDL2_TTF),yy)
 FFT_EVAL_CONV_OPTS += CONFIG_fft_eval_sdl=y
 FFT_EVAL_DEPENDENCIES += sdl2 sdl2_ttf
-FFT_EVAL_TARGETS += fft_eval_sdl
 else
 FFT_EVAL_CONV_OPTS += CONFIG_fft_eval_sdl=n
 endif