RFR(T) 8217319: Cleanup Shenandoah includes

[Zhengyu Gu]

Please review this trivial cleanup, that removes includes of .hpp files 
if corresponding .inline.hpp files are also included.

Bug: https://bugs.openjdk.java.net/browse/JDK-8217319
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8217319/webrev.00/

Test:
   PCH and none PCH builds
   tier1, 2, 3 gc_shenandoah on Linux x64

Thanks,

-Zhengyu