target.mk: Fix features detection for PWM

kmod-leds-pwm depends on @PWM_SUPPORT, instead of adding pwm to the
features env for specific targets, use the existing detection method.

Signed-off-by: Weikai Kong <[email protected]>
Link: openwrt/openwrt#18185
Signed-off-by: Robert Marko <[email protected]>

Author: PIPIPIG233666

include/target.mk

@@ -314,6 +314,9 @@ ifeq ($(DUMP),1)
     ifneq ($(CONFIG_PCIEPORTBUS),)
       FEATURES += pcie
     endif
+    ifneq ($(CONFIG_PWM),)
+      FEATURES += pwm
+    endif
     ifneq ($(CONFIG_USB)$(CONFIG_USB_SUPPORT),)
       ifneq ($(CONFIG_USB_ARCH_HAS_HCD)$(CONFIG_USB_EHCI_HCD),)
         FEATURES += usb