power: exynos-tmu: fix warnings and clean up code

This patch does the folowing
1. change the data types for unsigned int variable to unsigned
2. change the tmu_base type to struct exynos5_tmu_reg *
3. Add timer functionality for get_cur_temp()
4. error handling in the get_tmu_fdt_values()
5. Add check for curr_temp reading
6. some cosmotic changes.

Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Reviewed-by: Vadim Bendebury <vbendeb@google.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>