cpufreq: davinci: move configuration to include/linux/platform_data
The header containing the configuration structure for davinci cpufreq
driver lives in mach-davinci/include/mach/. This is fine for now but
if we want to make davinci part of the multi_v5 build, no code external
to mach-davinci should include machine-specific headers.
Move the configuration structure to include/linux/platform_data.
While we're at it: convert the GPL-2.0 boilerplate to a proper SPDX
license identifier.