liblog: fix header guards ordering

__ANDROID_API__ isn't defined on host, so this check will fail due to
-Wundef.  The || is short circuited through, so we can check for host
first and only have the right side of the || evaluated for device
builds.

Bug: 150898477
Bug: 151255209
Test: build
Change-Id: I2e0bc055ac0c7ba8262875801cdaed9cc30d2cef