Port "linear.cpp (check_parameter): only check value of p if L2R_L2LOSS_SVR."

Ported from cjlin1/liblinear@13d4a25

Author: bwaldvogel

src/main/java/de/bwaldvogel/liblinear/Linear.java

@@ -2056,7 +2056,7 @@ public static Model train(Problem prob, Parameter param) {
         if (param.C <= 0) {
             throw new IllegalArgumentException("C <= 0");
         }
-        if (param.p < 0) {
+        if (param.p < 0 && param.solverType == L2R_L2LOSS_SVR) {
             throw new IllegalArgumentException("p < 0");
         }