i2c: sh_mobile: simplify code and remove false compilation warning

i2c: sh_mobile: simplify code and remove false compilation warning

This currently generates a warning:

drivers/i2c/busses/i2c-sh_mobile.c: In function 'sh_mobile_i2c_isr':
drivers/i2c/busses/i2c-sh_mobile.c:399:26: warning: 'data' may be used uninitialized in this function [-Wmaybe-uninitialized]

Though the code looks okay and shouldn't ever use the variable
uninitialized. Fix the warning by moving the code around and getting rid
of 'data'.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
[wsa: minor updates to commit message]
Signed-off-by: Wolfram Sang <wsa@kernel.org>