MX28: Fix a typo in mx28_reg_8 macro
The macro mistakenly referred to 32bit struct instead of 8bit one.
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Marek Vasut <marex@denx.de>
Acked-by: Marek Vasut <marex@denx.de>