panfrost: Move pan_afbc.c file to the the right Makefile.source file

It seems pan_afbc.c was added to the wrong Makefile.sources file.

So fix this, so we don't run into build issues with mesa/master
trying to build under AOSP.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4141>

src/gallium/drivers/panfrost/Makefile.sources

@@ -3,7 +3,6 @@ C_SOURCES := \
 	nir/nir_lower_blend.h \
 	nir/nir_lower_framebuffer.c \
     \
-	pan_afbc.c \
 	pan_allocate.c \
 	pan_allocate.h \
 	pan_assemble.c \

src/panfrost/Makefile.sources

@@ -14,6 +14,7 @@ bifrost_FILES := \
         bifrost/disassemble.h
 
 encoder_FILES := \
+	encoder/pan_afbc.c \
         encoder/pan_attributes.c \
         encoder/pan_encoder.h \
         encoder/pan_invocation.c \