HF3D: Make space in ITC_RAM for more RPM filters

Lots of source files are compiled with speed optimisation,
which includes loop unrolling. This is filling up ITC_RAM
quickly. Let's disable speed optimisation on some files to
save up ITC_RAM for RPM filters. These files are still compiled
with optimisation, just without size implications.

make/source.mk

@@ -224,14 +224,6 @@ SPEED_OPTIMISED_SRC := $(SPEED_OPTIMISED_SRC) \
             drivers/timer.c \
             fc/core.c \
             fc/tasks.c \
-            fc/rc.c \
-            fc/rc_controls.c \
-            fc/runtime_config.c \
-            flight/gyroanalyse.c \
-            flight/imu.c \
-            flight/mixer.c \
-            flight/pid.c \
-            flight/rpm_filter.c \
             rx/ibus.c \
             rx/rx.c \
             rx/rx_spi.c \