Use SPDX license identifiers ...

To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.

NOTE: Files that have been imported by FreeBSD have not been modified.

[0]: https://spdx.org/

Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

emmc/sd: for C99 compliance, changed the unsigned char/short bitfield to unsigned int bitfields ...

C99 restricts bitfields type is signed and unsigned integer or _Bool.
See section 6.7.2.1 Structure and union specifiers.
"A bit-field shall have a type that is a qualified or unqualified version
 of _Bool, signed int, unsigned int, or some other implementation-defined type."

Since the compiler packs bitfields anyways, actual data layout in the structure is unaffected.

Signed-off-by: Alex Nemirovsky <alex.nemirovsky@cortina-access.com>

emmc: support CMD23 ...

Support CMD23. When CMD23 is used, CMD12 could be avoided.

Two scenarios:
1. CMD17 for single block, CMD18 + CMD12 for multiple blocks.
2. CMD23 + CMD18 for both single block and multiple blocks.

The emmc_init() should initialize whether CMD23 is supported
or not.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>

drivers: add emmc stack ...

In a lot of embedded platforms, eMMC device is the only one storage
device. So loading content from eMMC device is required in ATF.

Create the emmc stack that could co-work with IO block driver.
Support to read/write/erase eMMC blocks on both rpmb and normal
user area. Support to change the IO speed and bus width.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>