Rename BSP_DIR to PLATFORM

Updates references to CONFIG_BSP_DIR to CONFIG_PLATFORM as part of the
BSP -> platform clean up.

Note that despite the renaming, the usage of the config option remains
unchanged.

Change-Id: I2846c3f761cf09871019c0855bf1824ae03e6b3c
Signed-off-by: Peter Mitsis <peter.mitsis@windriver.com>
36 files changed