imx_common: Return MMCSD_MODE_FS in spl_boot_mode() also for EXTFS
spl_boot_mode() returned MMCSD_MODE_RAW on MMC if CONFIG_SPL_EXT_SUPPORT
was configured. EXTFS is the default filesystem selected in imx6_spl.h
and the function should return MMCSD_MODE_FS instead.
Fix this and return MMCSD_MODE_FS instead in such cases.
Signed-off-by: Petr Kulhavy <brain@jikos.cz> CC: Stefano Babic <sbabic@denx.de> CC: Tim Harvey <tharvey@gateworks.com> CC: Fabio Estevam <Fabio.Estevam@freescale.com>
