Revert "driver/serial : Fixed unwanted disabling of TX Interrupt"
Revert "driver/serial : Fixed unwanted disabling of TX Interrupt"

This reverts commit 66286dffd944783f4061fecde4f1c753e6ebace5.

jsdosa/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT