RFR(xs): 8042209: Remove unused function G1SATBCardTableLoggingModRefBS::write_ref_field_static

[Per Liden]

Hi,

This patch removes the unused function 
G1SATBCardTableLoggingModRefBS::write_ref_field_static().

There's also a static interface for the G1 pre-barrier, 
G1SATBCardTableModRefBS::write_ref_field_pre_static(), which is also 
unused except for a single use in the same header file. This patch 
removes the static interface and moves the code into the non-static 
version. The rational for this is to have the pre- and post- interfaces 
aligned.

Bug: https://bugs.openjdk.java.net/browse/JDK-8042209
Webrev: http://cr.openjdk.java.net/~pliden/8042209/webrev.0/
Testing: jprt builds on all platforms

/Per