env_ubi.c: Correct pointer error in env load

env_ubi.c: Correct pointer error in env load

The variable "buf" in this function is a char array, and the
function ubi_volume_read is expecting a char *.  In the call, the
address of the pointer is being taken, incorrectly passing a
char **.  The compiler warning was being silenced by the cast.
Remove the address operator and the cast.

Signed-off-by: Kevin Smith <[email protected]>
Cc: Joe Hershberger <[email protected]>
Cc: Tom Rini <[email protected]>
Acked-by: Joe Hershberger <[email protected]>
Reviewed-by: Heiko Schocher <[email protected]>