fix(rockchip64-7.0): drop SysRq-via-BREAK patch, fixed upstream in 7.0.12

The general-serial-8250-fix-sysrq-break-dw-apb patch no longer applied
against 7.0.12 (both hunks rejected); it was last rebased on 7.0.7.

Upstream 7.0.12 fixes the same regression itself by introducing the
uart_port_lock_check_sysrq_irqsave guard, which captures the SysRq
character on unlock. Both dw8250_handle_irq() and serial8250_handle_irq()
now use it -- the upstream equivalent of what this patch did manually via
uart_unlock_and_check_sysrq_irqrestore(). The patch is therefore redundant
and re-rolling would double-handle SysRq, so drop it.

Author: igorpecovnik