Instead of hard-coding the uart register addresses for the imx51, use
a variable that defaults to the imx51 address. When debugging another
imx-family SoC, the variable can be set early in initarm() to provide
full console/printf support for debugging early boot.
sys/arm and sys/mips), squelching the clang 3.3 warnings about this.
Noticed by: tinderbox and many irate spectators
Submitted by: Luiz Otavio O Souza <loos.br@gmail.com>
PR: kern/177759
MFC after: 3 days
