thermal: armada: Fix -Wshift-negative-value

Clang produces the following warning

drivers/thermal/armada_thermal.c:270:33: warning: shifting a negative
signed value is undefined [-Wshift-negative-value]
1 warning        reg &= ~CONTROL1_TSEN_AVG_MASK <<
CONTROL1_TSEN_AVG_SHIFT; generated
.
               ~~~~~~~~~~~~~~~~~~~~~~~ ^

CONTROL1_TSEN_AVG_SHIFT is defined to be zero.
Since shifting by zero does nothing this variable can be removed.

Cc: clang-built-linux@googlegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/532


Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>