clocksource: Fix clocksource_mmio_readX_down
clocksource: Fix clocksource_mmio_readX_down

For some clocksource devices, for example, the registers are 32-bit, while
the lower 16-bit is used for timer counting(And reading the upper 16-bit
will return 0).

For example, when the counter value is 0x00001111, and then the
~readl_relaxed(to_mmio_clksrc(c)->reg) will return the value of 0xFFFFEEEE,
but it should be 0x0000EEEE.

So just using the c->mask to mask the unused bits.

Signed-off-by: Xiubo Li <cf2f21a5d63bafab3dac1a48e01d31cd0b77ab89@freescale.com>
Signed-off-by: Daniel Lezcano <e9fa45941f2ebe89c1b9d6c5f339ab42eadb8567@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs