clk: samsung: add infrastructure to register cpu clocks

The CPU clock provider supplies the clock to the CPU clock domain. The
composition and organization of the CPU clock provider could vary among
Exynos SoCs. A CPU clock provider can be composed of clock mux, dividers
and gates. This patch defines a new clock type for CPU clock provider and
adds infrastructure to register the CPU clock providers for Samsung
platforms.

Changes by Bartlomiej:
- fixed issue with setting lower dividers before the parent clock speed
  was lowered (the issue resulted in lockup on Exynos4210 SoC based
  Origen board when "ondemand" cpufreq governor was stress tested)
- fixed missing spin_unlock on error in exynos_cpuclk_post_rate_change()
  problem by moving cfg_data search outside of the spin locked area
- removed leftover kfree() in exynos_register_cpu_clock() that could
  result in dereferencing the NULL pointer on error
- moved spin_lock earlier in exynos_cpuclk_pre_rate_change() to cover
  reading of E4210_SRC_CPU and E4210_DIV_CPU1 registers
- added missing "last chance" checks to wait_until_divider_stable() and
  wait_until_mux_stable() (needed in case that IRQ handling took long
  time to proceed and resulted in function printing incorrect error
  message about timeout)
- moved E4210_CPU_DIV[0,1]() macros just before their only users,
  this resulted in moving them from patch #2 to patch #3/6 ("clk:
  samsung: exynos4: add cpu clock configuration data and instantiate
  cpu clock")
- removed E5250_CPU_DIV[0,1](), E5420_EGL_DIV0() and E5420_KFC_DIV()
  macros for now
- added my Copyrights to drivers/clk/samsung/clk-cpu.c

Cc: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>