MIPS: powertv: Drop BOOTLOADER_DRIVER Kconfig symbol

The kbldr.h header file required for this was neither committed in the
original submission in a3a0f8c8ed2e2470f4dcd6da95020d41fed84747
"MIPS: PowerTV: Base files for Cisco PowerTV platform"
nor was it ever present in the git tree so this option never worked.
Fixes the following build problem:
arch/mips/powertv/reset.c:25:36: fatal error: asm/mach-powertv/kbldr.h: No such
file or directory
compilation terminated.

Cc: David VomLehn <dvomlehn@cisco.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Acked-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: David VomLehn <dvomlehn@cisco.com>
Patchwork: https://patchwork.linux-mips.org/patch/5801/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>