Remove unwanted space characters from dialing number

Certain car kits might send an AT command with space characters in
the dialing number. This commit adds a workaround to trim these unwanted
space characters.

Bug: 6340999
Test: Manual test with a car kit but purposely added numbers with spaces.
Change-Id: I9c238bc625fff8503c45cbbfaeb8bdd15b8a7d9a