MA-14501[Android] change BOOTAUX_RESERVED_MEM macro to defconfig

MA-14501[Android] change BOOTAUX_RESERVED_MEM macro to defconfig

As the M4 use different DDR memory size in normal android/car2 and car
image, use different defconfig for car2 to decrease DDR memory
reservation. So memory reserved for each M4 core is 8MB in car2 and
normal android image. it's 32MB for car image.

Change-Id: Idf608f539cd614a154c78e3a1af28eff1da5c1f2
Signed-off-by: Zhang Bo <bo.zhang@nxp.com>
Signed-off-by: Ye Li <ye.li@nxp.com>