Remove name length limit for system properties

Android O removes name length limit for system properties.

Use __system_property_read_callback instead of deprecated
__system_property_read in getprop and remove check for
property name length in setprop.

Test: adb shell setprop debug.test.very.very.long.property.name valueforpropertywithlongname
Test: adb shell getprop | grep debug.test.very.very.long.property.name
Bug: http://b/33926793
Change-Id: I57ca99ea33283d069cd1b7b9f110ec9fb27f3d19
2 files changed