[U-Boot] u-boot-mmc fails on almost every Tegra board

[Stephen Warren]

Jaehoon,

The latest commit in u-boot-mmc.git master branch fails on almost every 
Tegra board. The MMC device experiences an error during initialization 
and hence isn't available:

U-Boot 2018.01-05974-gb9b4f146c9 (Jan 22 2018 - 09:18:42 -0700), Build: 
jenkins-u-boot-denx_uboot_mmc-master-build-U_BOOT_BOARD=p2371-2180-151

TEGRA210
Model: NVIDIA P2371-2180
Board: NVIDIA P2371-2180
DRAM:  3.5 GiB
MMC:   sdhci at 700b0000: 1, sdhci at 700b0600: 0
tegra_mmc_send_cmd_bounced: waiting for status update
mmc_init: -110, time 1068
*** Warning - No block device, using default environment