uboot-imx

MA-14916-1 adapt to the directory change of libavb

libavb is now under the directory of lib/, not lib/avb/ as before, to
adapt to this change, some modifications are made:
1. header file inclusion change, including parameter of -I option in
Makefile
2. remove avb_sysdeps_posix.o in Makefile since the functions in
avb_sysdeps_posix.c has beed redefined in fsl_avb_sysdeps_uboot.c

Change-Id: I4216e3ddb4e3e810783e4f46b953eda510c2627b
Signed-off-by: faqiang.zhu <faqiang.zhu@nxp.com>