rtc: remove broken rtc_read and rtc_write declarations

rtc: remove broken rtc_read and rtc_write declarations

commit 04e11cf3 "rtc: add support for 4543 RTC (manufactured by e.g.
EPSON)" introduces the following build error on boards configuring e.g,
the ds1374 rtc:

Configuring for MPC837XEMDS board...
ds1374.c:103: error: static declaration of 'rtc_read' follows non-static declaration
/home/r1aaha/git/u-boot/include/rtc.h:64: error: previous declaration of 'rtc_read' was here
ds1374.c:104: error: conflicting types for 'rtc_write'
/home/r1aaha/git/u-boot/include/rtc.h:65: error: previous declaration of 'rtc_write' was here

this reverts the erroneous chunk.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Acked-by: Detlev Zundel <dzu@denx.de>
CC: Detlev Zundel <dzu@denx.de>
CC: Andreas Pfefferle <ap@denx.de>