DVDInterface: Remove VolumeIsValid

It's the same as IsDiscInside.

Source/Core/Core/Boot/Boot.cpp

@@ -50,7 +50,7 @@ bool CBoot::DVDRead(u64 dvd_offset, u32 output_address, u32 length, bool decrypt
 
 void CBoot::Load_FST(bool _bIsWii)
 {
-  if (!DVDInterface::VolumeIsValid())
+  if (!DVDInterface::IsDiscInside())
     return;
 
   const DiscIO::IVolume& volume = DVDInterface::GetVolume();
@@ -267,7 +267,7 @@ bool CBoot::BootUp()
   case SConfig::BOOT_ISO:
   {
     DVDInterface::SetVolumeName(_StartupPara.m_strFilename);
-    if (!DVDInterface::VolumeIsValid())
+    if (!DVDInterface::IsDiscInside())
       return false;
 
     const DiscIO::IVolume& pVolume = DVDInterface::GetVolume();
@@ -336,7 +336,7 @@ bool CBoot::BootUp()
     {
       BS2Success = EmulatedBS2(dolWii);
     }
-    else if ((!DVDInterface::VolumeIsValid() ||
+    else if ((!DVDInterface::IsDiscInside() ||
               DVDInterface::GetVolume().GetVolumeType() != DiscIO::Platform::WII_DISC) &&
              !_StartupPara.m_strDefaultISO.empty())
     {

Source/Core/Core/Boot/Boot_BS2Emu.cpp

@@ -67,7 +67,7 @@ bool CBoot::EmulatedBS2_GC(bool skipAppLoader)
   // to 0x80000000 according to YAGCD 4.2.
 
   // It's possible to boot DOL and ELF files without a disc inserted
-  if (DVDInterface::VolumeIsValid())
+  if (DVDInterface::IsDiscInside())
     DVDRead(/*offset*/ 0x00000000, /*address*/ 0x00000000, 0x20, false);  // write disc info
 
   PowerPC::HostWrite_U32(0x0D15EA5E,
@@ -100,7 +100,7 @@ bool CBoot::EmulatedBS2_GC(bool skipAppLoader)
 
   HLE::Patch(0x81300000, "OSReport");  // HLE OSReport for Apploader
 
-  if (!DVDInterface::VolumeIsValid())
+  if (!DVDInterface::IsDiscInside())
     return false;
 
   // Load Apploader to Memory - The apploader is hardcoded to begin at 0x2440 on the disc,
@@ -255,7 +255,7 @@ bool CBoot::SetupWiiMemory(u64 ios_title_id)
   */
 
   // When booting a WAD or the system menu, there will probably not be a disc inserted
-  if (DVDInterface::VolumeIsValid())
+  if (DVDInterface::IsDiscInside())
     DVDRead(0x00000000, 0x00000000, 0x20, false);  // Game Code
 
   Memory::Write_U32(0x0D15EA5E, 0x00000020);            // Another magic word
@@ -306,7 +306,7 @@ bool CBoot::SetupWiiMemory(u64 ios_title_id)
 bool CBoot::EmulatedBS2_Wii()
 {
   INFO_LOG(BOOT, "Faking Wii BS2...");
-  if (!DVDInterface::VolumeIsValid())
+  if (!DVDInterface::IsDiscInside())
     return false;
 
   if (DVDInterface::GetVolume().GetVolumeType() != DiscIO::Platform::WII_DISC)