env: clean env_embedded.c checkpatch and code style

Cleanup the env_embedded.c checkpatch warnings, errors and coding style.
There is one error left though:
 ERROR: Macros with multiple statements should be enclosed in a do - while loop
 #79: FILE: u-boot/common/env_embedded.c:79:
 +#define GEN_ABS(name, value)                   \
 +       asm(".globl " GEN_SYMNAME(name));       \
 +       GEN_SET_VALUE(name, value)

 total: 1 errors, 0 warnings, 213 lines checked

We cannot enclose that statement in a do - while loop,
because these are a global assembly declarations.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>