Only check the least bit of status byte for EF_SMS free space

According to 3GPP 51.011 10.5.3 & 3GPP2 C.S0023 3.4.27,
Only the least bit (b1) of status byte should be used to judge free space of EF_SMS.

Bug: 113093468
Test: make & manual test
Change-Id: I3e4b546ef12d7b054594db1d7cc4a1d5e25e6b69