drivers/spi: add IS_ENABLED() around Kconfig symbol references

Some of these can be changed from #if to if(), but that will happen
in a follow-on commmit.

Change-Id: If80e0c4e1c9911b44853561b03aef1c741255229
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20339
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/drivers/spi/eon.c

@@ -95,7 +95,7 @@ static int eon_write(const struct spi_flash *flash,
 		cmd[2] = (offset >> 8) & 0xff;
 		cmd[3] = offset & 0xff;
 
-#if CONFIG_DEBUG_SPI_FLASH
+#if IS_ENABLED(CONFIG_DEBUG_SPI_FLASH)
 		printk(BIOS_SPEW,
 		    "PP: 0x%p => cmd = { 0x%02x 0x%02x%02x%02x } chunk_len = %zu\n",
 		     buf + actual, cmd[0], cmd[1], cmd[2], cmd[3], chunk_len);
@@ -117,7 +117,7 @@ static int eon_write(const struct spi_flash *flash,
 		offset += chunk_len;
 	}
 
-#if CONFIG_DEBUG_SPI_FLASH
+#if IS_ENABLED(CONFIG_DEBUG_SPI_FLASH)
 	printk(BIOS_SPEW, "SF: EON: Successfully programmed %zu bytes @ %#x\n",
 	       len, (unsigned int)(offset - len));
 #endif