Use explicit .c_str() for hidl_string

hidl_string no longer will provide an implicit cast to const char* as it
interfers with other expected behaviors of the class.  It now emulated
std::string in requiring a call to .c_str() to get the same behavior.

Bug:  36532780
Test:  Build the tree
Change-Id: I2ce4354619a99d7c5ae8b39762d5506891ccd1ed

libwvdrmengine/mediacrypto/src_hidl/WVCryptoPlugin.cpp

@@ -56,7 +56,7 @@ WVCryptoPlugin::WVCryptoPlugin(const void* data, size_t size,
 
 Return<bool> WVCryptoPlugin::requiresSecureDecoderComponent(
     const hidl_string& mime) {
-  if (!strncasecmp(mime, "video/", 6)) {
+  if (!strncasecmp(mime.c_str(), "video/", 6)) {
     // Type is video, so query CDM to see if we require a secure decoder.
     CdmQueryMap status;