layoutlib: Use wildcard to find device overlays

The layoutlib_data.mk file uses `$(shell find ...)` to locate
device-specific framework overlays for a hardcoded list of products.

When a user's source tree does not contain all of these device
directories, the `find` command outputs a "No such file or directory"
error for each missing path, spamming the build log.

Replace the `shell find` call with the idiomatic GNU Make `wildcard`
function. `wildcard` correctly finds all existing files that match
the patterns without generating errors for non-existent paths.

This cleans up the build output and is slightly more efficient as it
avoids forking a shell process.

Change-Id: I2f4d6c593b073bd3955c0fd88d2cc699526e261c
Signed-off-by: Dmitrii <bankersenator@gmail.com>