package/bdwgc: bump version to 7.6.0

package/bdwgc: bump version to 7.6.0

Removed patches applied upstream:

0002-Do-not-include-sigcontext.h-and-asm-sigcontext.h.patch
https://github.com/ivmai/bdwgc/commit/c887470e0e3310c81ecdb7e736bc5d2ead45db2a

0003-Revert-Move-asm-machine-dependent-files-to-src-folde.patch
https://github.com/ivmai/bdwgc/commit/5e756d4d8df2949cb3b6e51532d3016cbb276fd7

0004-configure-match-uclinux-pattern.patch
https://github.com/ivmai/bdwgc/commit/a628c90bdbf397465ac2ab2b11f14eb2e853651c

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>