Rename efi_fb to efi_uga.
* conf/i386-efi.rmk (pkglib_MODULES): Rename 'efi_fb.mod' to
'efi_uga.mod'.
(efi_fb_mod_SOURCES): Rename this ...
(efi_uga_mod_SOURCES): ... to this.
(efi_fb_mod_CFLAGS): Rename this ...
(efi_uga_mod_CFLAGS): ... to this.
(efi_fb_mod_LDFLAGS): Rename this ...
(efi_uga_mod_LDFLAGS): ... to this.
* conf/x86_64-efi.rmk (pkglib_MODULES): Rename 'efi_fb.mod' to
'efi_uga.mod'.
(efi_fb_mod_SOURCES): Rename this ...
(efi_uga_mod_SOURCES): ... to this.
(efi_fb_mod_CFLAGS): Rename this ...
(efi_uga_mod_CFLAGS): ... to this.
(efi_fb_mod_LDFLAGS): Rename this ...
(efi_uga_mod_LDFLAGS): ... to this.
* video/efi_fb.c: Move this ...
* video/efi_uga.c: ... to this. Change prefix to 'grub_video_uga_'.