target/riscv: drop unused variable registers_initialized

Change-Id: If7bfe38ac273ce9e54003e003807e128cced1568
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: https://review.openocd.org/c/openocd/+/6995
Tested-by: jenkins
Reviewed-by: Tim Newsome <tim@sifive.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/riscv/riscv.h

@@ -118,9 +118,6 @@ typedef struct {
 	/* The number of entries in the debug buffer. */
 	int debug_buffer_size;
 
-	/* This avoids invalidating the register cache too often. */
-	bool registers_initialized;
-
 	/* This hart contains an implicit ebreak at the end of the program buffer. */
 	bool impebreak;