mmc: update MMC_ERASE argument to match Linux kernel.

Table 41 of the JEDEC standard for eMMC says that bit 31 of
the command argument is obsolete when issuing the ERASE
command (CMD38) on page 115 of this document:
	http://www.jedec.org/sites/default/files/docs/jesd84-B45.pdf

The SD Card Association Physical Layer Simplified Specification also
makes no mention of the use of bit 31.
	https://www.sdcard.org/downloads/pls/part1_410.pdf



The Linux kernel distinguishes between secure (bit 31 set) and
non-secure erase, and this patch copies the macro names from
include/linux/mmc/core.h.

Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Eric Nelson <eric@nelint.com>
Tested-by: Hector Palacios <hector.palacios@digi.com>