net: wireless: rtl8192cu: Import alternative driver

This is the driver from Realtek itself, with updates from various
people.

Source: https://github.com/dz0ny/rt8192cu/

Removed CR end-of-line characters and a few other unprintable
characters from the sources.
Selected CONFIG_PLATFORM_MIPS_JZ4760 in the Makefile.
Appended "_ALT" to the main config variable name "CONFIG_RTL8192CU", so
this driver can exist in the same source tree as the mainline driver.
net: wireless: rtl8192cu: Fixed usage of kthread_run

The returned value is a pointer to a struct, not an integer.

This fixes driver init on MIPS, where pointers are likely to be
negative when interpreted as an integer (since they are allocated
in kseg0).