clk: make strings in parent name arrays const

The clk functions and structs declare the parent_name arrays as
'const char **parent_names' which means the parent name strings
are const, but the array itself is not. Use
'const char * const * parent_names' instead which also makes
the array const. This allows us to put the parent_name arrays into
the __initconst section.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
[sboyd@codeaurora.org: Squelch 80-character checkpatch warnings]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>