Remove unused system/nativepower.

This repo is not used anymore.
Bug: 35804180
Test: repo sync; make checkbuild
(cherry picked from commit b29a19b7c18c7eaf1dd706f6489e8b93b5c461d0)
Change-Id: I77dddc2cfe5e148e6f5225eceae4bf039f684ca5

default.xml

@@ -539,7 +539,6 @@
   <project path="system/libufdt" name="platform/system/libufdt" groups="pdk" />
   <project path="system/libvintf" name="platform/system/libvintf" groups="pdk" />
   <project path="system/media" name="platform/system/media" groups="pdk" />
-  <project path="system/nativepower" name="platform/system/nativepower" />
   <project path="system/netd" name="platform/system/netd" groups="pdk" />
   <project path="system/nfc" name="platform/system/nfc" groups="pdk" />
   <project path="system/nvram" name="platform/system/nvram" />