i2c: tegra: check the clk_prepare_enable() return value

i2c: tegra: check the clk_prepare_enable() return value

commit 132c803f7b70b17322579f6f4f3f65cf68e55135 upstream.

NVIDIA's Tegra SoC allows read/write of controller register only
if controller clock is enabled. System hangs if read/write happens
to registers without enabling clock.

clk_prepare_enable() can be fail due to unknown reason and hence
adding check for return value of this function. If this function
success then only access register otherwise return to caller with
error.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
[bwh: Backported to 3.2:
 - Adjust context
 - Keep calling clk_enable() directly]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>