hwmon: (lm95241) Check validity of input values

This clears the following build-time warnings I was seeing:

drivers/hwmon/lm95241.c: In function "set_interval":
drivers/hwmon/lm95241.c:132:15: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result
drivers/hwmon/lm95241.c: In function "set_max2":
drivers/hwmon/lm95241.c:278:1: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result
drivers/hwmon/lm95241.c: In function "set_max1":
drivers/hwmon/lm95241.c:277:1: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result
drivers/hwmon/lm95241.c: In function "set_min2":
drivers/hwmon/lm95241.c:249:1: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result
drivers/hwmon/lm95241.c: In function "set_min1":
drivers/hwmon/lm95241.c:248:1: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result
drivers/hwmon/lm95241.c: In function "set_type2":
drivers/hwmon/lm95241.c:220:1: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result
drivers/hwmon/lm95241.c: In function "set_type1":
drivers/hwmon/lm95241.c:219:1: warning: ignoring return value of "strict_strtol", declared with attribute warn_unused_result

This also fixes a small race in set_interval() as a side effect: by
working with a temporary local variable we prevent data->interval from
being accessed at a time it contains the interval value in the wrong
unit.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Davide Rizzo <elpa.rizzo@gmail.com>