buildroot

orangepipc: rename to orangepi-pc

Rename orangepipc files, configs, and directories:
- oragepipc_defconfig -> orangepi_pc_defconfig
- board/orangepi/orangepipc -> board/orangepi/orangepi-pc

The purpose of the patch is to improve readability before
adding other boards of orangepi family.

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>