AndroidBoard.mk: fix wrong indentation

As tabs are used for indicating shell commands, this breaks in some
cases and leads to the following error:

[100% 881/881] build droidcore
FAILED: droidcore
/bin/bash -c "KERNEL_DEFCONFIG := msm8953_defconfig"
/bin/bash: KERNEL_DEFCONFIG: command not found
10:27:01 ninja failed with: exit status 1

Issue: FP3-A11#40
Change-Id: I33481212fe47f413efe3818e1d143efa6c65a642
1 file changed