[GCC4] fix build error in drivers/char/drm-4.0/drmP.h

[GCC4] fix build error in drivers/char/drm-4.0/drmP.h

This patch fixes these errors with gcc 4 :

gamma_drv.c: In function 'gamma_setup':
gamma_drv.c:191: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_takedown':
gamma_drv.c:210: error: expected ')' before '__FUNCTION__'
gamma_drv.c:258: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_init':
gamma_drv.c:348: error: expected ')' before '__FUNCTION__'
gamma_drv.c:361: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_cleanup':
gamma_drv.c:388: error: expected ')' before '__FUNCTION__'
gamma_drv.c:392: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_open':
gamma_drv.c:443: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_release':
gamma_drv.c:468: error: expected ')' before '__FUNCTION__'
gamma_drv.c:477: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_ioctl':
gamma_drv.c:510: error: expected ')' before '__FUNCTION__'
gamma_drv.c:520: error: expected ')' before '__FUNCTION__'
gamma_drv.c: In function 'gamma_unlock':
gamma_drv.c:546: error: expected ')' before '__FUNCTION__'
gamma_drv.c:551: error: expected ')' before '__FUNCTION__'
gamma_drv.c:562: error: expected ')' before '__FUNCTION__'