esp32/Makefile: Use system provided math library rather than uPy one.

The ESP IDF system already provides a math library, and that one is likely
to be better tuned to the Xtensa architecture.  The IDF components are also
tested against its own math library, so best not to override it.  Using the
system provided library also allows to easily switch to double-precision
floating point by changing MICROPY_FLOAT_IMPL to MICROPY_FLOAT_IMPL_DOUBLE.

ports/esp32/Makefile

@@ -182,24 +182,6 @@ EXTMOD_SRC_C = $(addprefix extmod/,\
 	)
 
 LIB_SRC_C = $(addprefix lib/,\
-	libm/math.c \
-	libm/fmodf.c \
-	libm/roundf.c \
-	libm/ef_sqrt.c \
-	libm/kf_rem_pio2.c \
-	libm/kf_sin.c \
-	libm/kf_cos.c \
-	libm/kf_tan.c \
-	libm/ef_rem_pio2.c \
-	libm/sf_sin.c \
-	libm/sf_cos.c \
-	libm/sf_tan.c \
-	libm/sf_frexp.c \
-	libm/sf_modf.c \
-	libm/sf_ldexp.c \
-	libm/asinfacosf.c \
-	libm/atanf.c \
-	libm/atan2f.c \
 	mp-readline/readline.c \
 	netutils/netutils.c \
 	timeutils/timeutils.c \