rtc: v3020: fix v3020_mmio_read_bit()

rtc: v3020: fix v3020_mmio_read_bit()

v3020_mmio_read_bit() always returns 0 when left_shift > 7.

v3020_mmio_read_bit()'s return type is (unsigned char).  The code returns
a value masked by (1 << left_shift) that is casted to the return type.  If
left_shift is larger than 7, the cast will always result in a 0 return
value.  The problem was discovered with left_shift = 16, and the included
patch corrects the problem.

The bug was introduced in the last (Apr 3 2009) commit of the file, kernel
versions 2.6.30 and later.

Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Raphael Assenat <raph@8d.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>