Fixing missing SPI include for tftbmp examples

Fixed the filename to line up with the [2.8"tft example](http://learn.adafruit.com/2-8-tft-touch-shield/bitmaps)

Without the SPI.h include the errors become:

````
Arduino: 1.5.4 (Windows NT (unknown)), Board: "Arduino Uno"

C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp: In function 'void spiSend(uint8_t)':
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp:54: error: 'SPI' was not declared in this scope
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp: In function 'uint8_t spiRec()':
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp:81: error: 'SPI' was not declared in this scope
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp: In member function 'uint8_t Sd2Card::init(uint8_t, uint8_t, int8_t, int8_t, int8_t)':
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp:326: error: 'SPI' was not declared in this scope
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp: In member function 'uint8_t Sd2Card::setSckRate(uint8_t)':
C:\Program Files (x86)\Arduino\libraries\SD\utility\Sd2Card.cpp:585: error: 'SPI' was not declared in this scope

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````