libm: add missing symbols to optimized math functions

add the following missing symbols to optimized math functions:
sqrtl => sqrt
sinl  => sin
cosl  => cos

these symbols will be weak references to the functions at
right-hand side when compiler internal macro
(__LDBL_MANT_DIG__ == 53) is true

Change-Id: Ie3b3e720b3207bbc13574b9b6d42738767f22754
3 files changed