system/readline: add preprocessor for global variable
system/readline: add preprocessor for global variable

This patch modifies the g_erasetoeol global variable to be included only
when CONFIG_READLINE_ECHO is enabled.

Change-Id: Ifa5b31287eea662f483f803bb42986088301d896
Signed-off-by: Heuisam Kwag <2145cbb01e90577cd4983eccc3b7d9a9dfba6875@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT