mtd: spi-nor-tiny: annotate switch/case fallthrough

The SPI NOR code uses an implicit switch/case fallthrough when checking
different vendors to determine how to deal with extended addressig modes.

Add our "fallthrough;" statement-like macro before some label in the
4-byte addressing mode code, to avoid a warning when GCC's
-Wimplicit-fallthrough warning option is enabled.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/mtd/spi/spi-nor-tiny.c b/drivers/mtd/spi/spi-nor-tiny.c
index 5755c5e..23de64a 100644
--- a/drivers/mtd/spi/spi-nor-tiny.c
+++ b/drivers/mtd/spi/spi-nor-tiny.c
@@ -219,6 +219,7 @@
 	case SNOR_MFR_MICRON:
 		/* Some Micron need WREN command; all will accept it */
 		need_wren = true;
+		fallthrough;
 	case SNOR_MFR_MACRONIX:
 	case SNOR_MFR_WINBOND:
 		if (need_wren)