Kernel: Clear TTY when setting as current

Actually this should replace from old buffer, but this works
for now.

kernel/include/kernel/Terminal/Serial.h

@@ -43,7 +43,8 @@ namespace Kernel
 		
 		virtual uint32_t width() const override;
 		virtual uint32_t height() const override;
-		virtual void putchar_impl(uint8_t) override;
+
+		virtual void clear() override { putchar_impl('\e'); putchar_impl('['); putchar_impl('2'); putchar_impl('J'); }
 
 		virtual void update() override;
 
@@ -51,6 +52,7 @@ namespace Kernel
 
 	protected:
 		virtual BAN::StringView name() const override { return m_name; }
+		virtual void putchar_impl(uint8_t) override;
 
 	private:
 		SerialTTY(Serial);

kernel/include/kernel/Terminal/TTY.h

@@ -38,7 +38,8 @@ namespace Kernel
 		virtual uint32_t height() const = 0;
 		virtual uint32_t width() const = 0;
 		void putchar(uint8_t ch);
-		virtual void putchar_impl(uint8_t ch) = 0;
+
+		virtual void clear() = 0;
 
 		virtual bool has_data_impl() const override;
 
@@ -47,6 +48,7 @@ namespace Kernel
 			: CharacterDevice(mode, uid, gid)
 		{ }
 
+		virtual void putchar_impl(uint8_t ch) = 0;
 		virtual BAN::ErrorOr<size_t> read_impl(off_t, void*, size_t) override;
 		virtual BAN::ErrorOr<size_t> write_impl(off_t, const void*, size_t) override;
 

kernel/include/kernel/Terminal/VirtualTTY.h

@@ -21,15 +21,16 @@ namespace Kernel
 
 		virtual uint32_t height() const override { return m_height; }
 		virtual uint32_t width() const override { return m_width; }
-		virtual void putchar_impl(uint8_t ch) override;
+
+		virtual void clear() override;
 
 	protected:
 		virtual BAN::StringView name() const override { return m_name; }
+		virtual void putchar_impl(uint8_t ch) override;
 
 	private:
 		VirtualTTY(TerminalDriver*);
 
-		void clear();
 		void reset_ansi();
 		void handle_ansi_csi(uint8_t ch);
 		void handle_ansi_csi_color();