poll() and select() should not be built if poll() is disabled

drivers/Kconfig

@@ -11,6 +11,9 @@ config DISABLE_POLL
 		supported.  If you do not use poll() or select(), then you can
 		select DISABLE_POLL to reduce the code footprint by a small amount.
 
+		This selection disables the poll() interface as well as interfaces
+		the derive from poll() such as select().
+
 config DEV_NULL
 	bool "Enable /dev/null"
 	default y

fs/vfs/Make.defs

@@ -41,7 +41,7 @@ ifneq ($(CONFIG_NSOCKET_DESCRIPTORS),0)
 
 # Socket descriptor support
 
-CSRCS += fs_close.c fs_read.c fs_write.c fs_ioctl.c fs_poll.c fs_select.c
+CSRCS += fs_close.c fs_read.c fs_write.c fs_ioctl.c
 
 # Support for network access using streams
 
@@ -49,6 +49,12 @@ ifneq ($(CONFIG_NFILE_STREAMS),0)
 CSRCS += fs_fdopen.c
 endif
 
+# Support for poll() and select() (which derives from poll()
+
+ifneq ($(CONFIG_DISABLE_POLL),y)
+CSRCS += fs_poll.c fs_select.c
+endif
+
 # Support for sendfile()
 
 ifeq ($(CONFIG_NET_SENDFILE),y)