ppc: enable FENV support in uClibc-ng config

target/ppc/uclibc-ng.config

@@ -62,6 +62,7 @@ UCLIBC_HAS_FLOATS=y
 UCLIBC_HAS_FPU=y
 DO_C99_MATH=y
 DO_XSI_MATH=y
+UCLIBC_HAS_FENV=y
 UCLIBC_HAS_LONG_DOUBLE_MATH=y
 KERNEL_HEADERS=""
 HAVE_DOT_CONFIG=y