You are correct. From the Google search.
Errors about char-major-10-135 refer to the character device, major 10, minor 135, which is /dev/rtc. It provides access to the BIOS clock, or RTC, the Real Time Clock. Check /usr/src/linux/Documentation/rtc.txt for more information.
Something, most likely hwclock, is trying to use it but you haven't configured kernel support for it in your kernel. Either delete /dev/rtc so hwclock won't try to use it or enable RTC support in your kernel. It's located in make menuconfig under "Character devices" -> "Enhanced Real Time Clock Support".