clk: bcm2835: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.

Cc: Simon Arlott <[email protected]>
Cc: Stephen Warren <[email protected]>
Signed-off-by: Stefan Wahren <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>
Signed-off-by: Stephen Boyd <[email protected]>
4 files changed