Do not set CONFIG_LSM_MMAP_MIN_ADDR; use the default.

This is the address limit for checking SELinux mmap_zero permission,
which predated the CAP_SYS_RAWIO check and intentionally uses
a fixed limit rather than /proc/sys/vm/mmap_min_addr to avoid being
mutable by userspace.

When we first enabled this in our kernels, we were conservative
and only set it to 4096.  However, since Android sets
/proc/sys/vm/mmap_min_addr to 32768, we should just use the default
value (also 32768 for ARM, 65536 for others) specified by security/Kconfig.
Remove the explicit setting of the value from the defconfig file.

Change-Id: I260f2477225be7d0a406d1ad25a83ebc36fd4996
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>