Rename LM3S files, variables, and types from lm3s_ to lm_; Rename...

Rename LM3S files, variables, and types from lm3s_ to lm_; Rename configuration variables from CONFIG_LM3S_ to CONFIG_LM_

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5497 42af7a65-404d-4744-a932-0658087f49c3