spi: Avoid checking console in SPL

When SPI flash is used in SPL there is no console, so ctrlc() cannot be
called. Add a condition to fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/mtd/spi/spi-nor-core.c

@@ -929,7 +929,7 @@ static int spi_nor_erase(struct mtd_info *mtd, struct erase_info *instr)
 
 	while (len) {
 		WATCHDOG_RESET();
-		if (ctrlc()) {
+		if (!IS_ENABLED(CONFIG_SPL_BUILD) && ctrlc()) {
 			addr_known = false;
 			ret = -EINTR;
 			goto erase_err;