V4L/DVB (7851): Fix FW_LOADER depencency at v4l/dvb

Since:
1) FW_LOADER is defined as:

config FW_LOADER
        tristate "Userspace firmware loading support"
        depends on HOTPLUG

2) several V4L/DVB driver just selects it;

3) select is not smart enough to auto-select HOTPLUG, if select FW_LOADER.

So, All drivers that select FW_LOADER should also depend on HOTPLUG.

An easier solution (for the end-user perspective) would be to "select HOTPLUG".
However, live is not simple. This would cause recursive dependency issues like
this one:

drivers/usb/Kconfig:62:error: found recursive dependency: USB -> USB_OHCI_HCD
-> I2C -> MEDIA_TUNER -> MEDIA_TUNER_XC2028 -> HOTPLUG -> PCCARD -> PCMCIA ->
USB_ARCH_HAS_HCD -> MOUSE_APPLETOUCH -> USB

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>