Error in function mmc_init with the usage of eMMC 5.1.
This was due to timing constrains. In fact, the returned value by this
function was -19.
Now there is no error during the eMMC initialization.

Symptoms of this error
- environment stored into eMMC not accessible
- mmc command line doesn't work

If in mmc_send_op_cond, OCR_BUSY is set in CMD1's response, then
state is transfered to Ready state, and there is no need to
send CMD1 again. Otherwise following CMD1 will recieve no response,
or timeour error from driver such as fsl_esdhc.c.

If not into Ready state in previous CMD1, then continue CMD1
command.

Log Before:
U-Boot 2014.04-gc89172f-dirty (Dec 05 2022 - 08:06:33)

CPU:   Freescale i.MX6SOLO rev1.3 at 792 MHz
CPU:   Temperature 33 C, calibration data: 0x5895185f
Reset cause: POR
Board: Seco uQ7-i.MX6 (uQ7-J) - A75
I2C:   ready
DRAM:  256 MiB
Boot: Unknow
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
MMC init failed
Using default environment
In:    serial
Out:   serial
Err:   serial

Log Now:
U-Boot 2014.04-gc89172f-dirty (Dec 05 2022 - 09:39:10)

CPU:   Freescale i.MX6SOLO rev1.3 at 792 MHz
CPU:   Temperature 46 C, calibration data: 0x5895185f
Reset cause: WDOG
Board: Seco uQ7-i.MX6 (uQ7-J) - A75
I2C:   ready
DRAM:  256 MiB
Boot: Unknow
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
In:    serial
Out:   serial
Err:   serial