[STM32L0XX] Remove stabilization of the timer

[svastm]

As we discussed here #1743 the stabilization of the timer for STM32L0 targets do not do the trick. Because it cause also the fail of MBED_23 for all the STM32L0 except NUCLEO_L073RZ, we should remove it.

+--------+---------------------+-----------+---------+------------------+--------------------+---------------+-------+
| Result | Target              | Toolchain | Test ID | Test Description | Elapsed Time (sec) | Timeout (sec) | Loops |
+--------+---------------------+-----------+---------+------------------+--------------------+---------------+-------+
| OK     | NUCLEO_L053R8[CA2B] | uARM      | MBED_23 | Ticker Int us    |        11.4        |       15      |  1/1  |
| OK     | NUCLEO_L073RZ[F55F] | uARM      | MBED_23 | Ticker Int us    |       11.37        |       15      |  1/1  |
| OK     | NUCLEO_L011K4[F4B9] | uARM      | MBED_23 | Ticker Int us    |       11.75        |       15      |  1/1  |
| OK     | NUCLEO_L031K6[C8AA] | uARM      | MBED_23 | Ticker Int us    |       11.35        |       15      |  1/1  |
+--------+---------------------+-----------+---------+------------------+--------------------+---------------+-------+

[0xc0170]

As we discussed here #1743 the stabilization of the timer for STM32L0 targets do not do the trick.

What does? is there still bug to be fixed?

[svastm]

To me, the fix without the stabilization is OK. I can't reproduce the initial bug. The stabilization make the first us_read fail and then put the first event in the past.

[0xc0170]

@mbed-bot: TEST

HOST_OSES=windows
BUILD_TOOLCHAINS=ARM,GCC_ARM,IAR
TARGETS=NUCLEO_L053R8

[mbed-bot]

[Build 574]
FAILURE: Something went wrong when building and testing.

[0xc0170]

Tests results matches the above results, LGTM