SPI: Add TSC2102 main SPI driver

This adds a driver for the TSC2102 chip by Texas Instruments. This
driver is responsible for all communication with the chip and doesn't
export anything for user-space, but for other drivers controlling
devices connected to the chip.

Signed-off-by: Andrzej Zaborowski <balrog@zabor.org>

diff --cc drivers/spi/Kconfig
Simple merge

diff --cc drivers/spi/Makefile
Simple merge

diff --cc drivers/spi/tsc2102.c
Simple merge

diff --cc include/linux/spi/tsc2102.h
Simple merge