[CHAR] lcd: Fix two warnings.

In file included from drivers/char/lcd.c:23:
include/linux/mc146818rtc.h:104:1: warning: "RTC_IO_EXTENT" redefined
drivers/char/lcd.c:15:1: warning: this is the location of the previous definition
drivers/char/lcd.c:35: warning: 'lcd_lock' defined but not used

c316eb1e deleted the last code using
lcd_lock, so delete definition of lcd_lock.

The definition of RTC_IO_EXTENT is unused and probably always was only
debree copied from drivers/char/rtc.c.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>