Staging: lustre: gfp_mask should be of gfp_t type

Fixed the following sparse complaints:

drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/ldlm_pool.c:1039:61:
	warning: restricted gfp_t degrades to integer
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/ldlm_pool.c:1092:61:
	warning: restricted gfp_t degrades to integer
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/ldlm_pool.c:1136:58:
	warning: incorrect type in argument 2 (different base types)
	expected unsigned int [unsigned] gfp_mask
	got restricted gfp_t [usertype] gfp_mask
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/ldlm_pool.c:1142:34:
	warning: incorrect type in argument 3 (different base types)
	expected unsigned int [unsigned] gfp_mask
	got restricted gfp_t [usertype] gfp_mask
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/ldlm_pool.c:1147:58:
	warning: incorrect type in argument 2 (different base types)
	expected unsigned int [unsigned] gfp_mask
	got restricted gfp_t [usertype] gfp_mask
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/ldlm_pool.c:1153:34:
	warning: incorrect type in argument 3 (different base types)
	expected unsigned int [unsigned] gfp_mask
	got restricted gfp_t [usertype] gfp_mask

Signed-off-by: Fabio Falzoi <fabio.falzoi84@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>