mmc: fsl_esdhc: update eMMC44 adapter card erase timeout

Freescale eMMC44 adapter card uses Micron N2M400FDB311A3CF eMMC
memory. According to the silicon datasheet, secure erase timeout
is 600ms. So increase erase timeout value from 250ms to 600ms.

Signed-off-by: Yangbo Lu <yangbo.lu@freescale.com>
Cc: York Sun <yorksun@freescale.com>