add coverage dir for xpu (#45630)

tools/coverage/paddle_coverage.sh

@@ -72,6 +72,7 @@ function gen_full_html_report() {
 function gen_full_html_report_xpu() {
     lcov --extract coverage.info \
         '/paddle/paddle/fluid/operators/*xpu*' \
+        '/paddle/paddle/phi/kernels/xpu/*' \
         -o coverage-full.tmp \
         --rc lcov_branch_coverage=0