bootloader_support: Rename include_priv directory to include_bootloader

Old rationale for "priv" no longer applies.

As reported here: https://esp32.com/viewtopic.php?f=13&t=6155&p=27151#p26601

components/bootloader_support/component.mk

@@ -1,10 +1,10 @@
 COMPONENT_ADD_INCLUDEDIRS := include
-COMPONENT_PRIV_INCLUDEDIRS := include_priv
 
 ifdef IS_BOOTLOADER_BUILD
-# share "private" headers with the bootloader component
-# eventual goal: all functionality that needs this lives in bootloader_support
-COMPONENT_ADD_INCLUDEDIRS += include_priv
+# share "include_bootloader" headers with bootloader main component
+COMPONENT_ADD_INCLUDEDIRS += include_bootloader
+else
+COMPONENT_PRIV_INCLUDEDIRS := include_bootloader
 endif
 
 COMPONENT_SRCDIRS := src