Remove unnecessary #def BTIF_DM_LE_KEY_

=>BTM_LE_KEY_

BTM_LE_KEY_PENC == BTA_LE_KEY_PENC == BTIF_DM_LE_KEY_PENC
BTM_LE_KEY_PID == BTA_LE_KEY_PID == BTIF_DM_LE_KEY_PID
BTM_LE_KEY_PCSRK == BTA_LE_KEY_PCSRK == BTIF_DM_LE_KEY_PCSRK

BTM_LE_KEY_LENC == BTA_LE_KEY_LENC == BTIF_DM_LE_KEY_LENC
BTM_LE_KEY_LID == BTA_LE_KEY_LID == BTIF_DM_LE_KEY_LID
BTM_LE_KEY_LCSRK == BTA_LE_KEY_LCSRK == BTIF_DM_LE_KEY_LCSRK

Towards fewer aliases

Bug: 163134718
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: I8e0acad049b7c5d816a5244825bcd0b9028e3a25