drivers/: Make 'fallback_{un}map' the default unless defined

Drop the explicit need to specify the default 'fallback_{un}map'
callback function pointer from the 'programmer_entry' struct.
This is a reasonable default for every other driver in the tree
with only a select few exceptions [atavia, serprog, dummyflasher
and internal].

Thus this simplifies driver development and paves way
to remove the 'programmer' global handle.

Change-Id: I5ea7bd68f7ae2cd4af9902ef07255ab6ce0bfdb3
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
---
M atahpt.c
M atapromise.c
M atavia.c
M buspirate_spi.c
M ch341a_spi.c
M dediprog.c
M developerbox_spi.c
M digilent_spi.c
M drkaiser.c
M flashrom.c
M ft2232_spi.c
M gfxnvidia.c
M it8212.c
M jlink_spi.c
M linux_mtd.c
M linux_spi.c
M mediatek_i2c_spi.c
M mstarddc_spi.c
M ni845x_spi.c
M nic3com.c
M nicintel.c
M nicintel_eeprom.c
M nicintel_spi.c
M nicnatsemi.c
M nicrealtek.c
M ogp_spi.c
M parade_lspcon.c
M pickit2_spi.c
M pony_spi.c
M raiden_debug_spi.c
M rayer_spi.c
M realtek_mst_i2c_spi.c
M satamv.c
M satasii.c
M serprog.c
M stlinkv3_spi.c
M usbblaster_spi.c
37 files changed, 28 insertions(+), 80 deletions(-)